MS&AD updates 15.8% stake in W. R. Berkley

Rhea-AI Filing Summary

MS&AD Insurance Group Holdings and Mitsui Sumitomo Insurance have amended their Schedule 13D for W. R. Berkley Corporation, confirming that Mitsui Sumitomo Insurance beneficially owns 58,780,450 common shares, or 15.8% of the shares outstanding as of April 27, 2026.

The filing explains that, because Mitsui Sumitomo is a wholly owned subsidiary, MS&AD may be deemed an indirect beneficial owner of these shares, though it disclaims beneficial ownership. It also notes a Framework Agreement under which Andrew Carrier, an MSI executive, was designated and elected as a director of W. R. Berkley on June 3, 2026.

The amendment further states that, through the Framework Agreement and related LLC Agreement, the reporting persons may be deemed to share voting power over 63,515,547 additional shares held by WR Berkley & Others LLC (Family Holdings), representing about 17.1% of the common stock, while expressly declining to admit they form a group with Family Holdings.

Insights

Equity ownership and governance analyst

Large strategic stake in W. R. Berkley clarified, with board representation formalized.

Mitsui Sumitomo Insurance (MSI) reports beneficial ownership of 58,780,450 W. R. Berkley common shares, representing 15.8% of shares outstanding as of April 27, 2026. As MSI’s parent, MS&AD Holdings may be deemed to own these shares indirectly but disclaims beneficial ownership.

The filing also highlights governance ties. Under a Framework Agreement, MSI designated executive Andrew Carrier to W. R. Berkley’s board, and he was elected on June 3, 2026. This embeds the strategic relationship at board level, though economic terms are not discussed here.

Additionally, the amendment notes that, via the Framework Agreement and an LLC Agreement, the reporting persons may be deemed to share voting power over 63,515,547 shares (about 17.1%) held by Family Holdings. The document explicitly states this is not an admission that they form a Rule 13d-5 group, so the precise coordination among holders remains a legal and practical nuance rather than a stated fact.

Key Figures

MSI beneficial ownership: 58,780,450 shares Ownership percentage (MSI): 15.8% Shares outstanding: 372,276,732 shares +3 more

6 metrics

MSI beneficial ownership 58,780,450 shares W. R. Berkley common stock beneficially owned by Mitsui Sumitomo Insurance

Ownership percentage (MSI) 15.8% Portion of W. R. Berkley common stock based on shares outstanding as of April 27, 2026

Shares outstanding 372,276,732 shares W. R. Berkley common stock outstanding as of April 27, 2026

Family Holdings ownership 63,515,547 shares Common shares of W. R. Berkley beneficially owned by WR Berkley & Others LLC

Family Holdings percentage 17.1% Approximate share of W. R. Berkley common stock held by Family Holdings as of March 5, 2026

Event date June 3, 2026 Date of event requiring the Schedule 13D amendment and board election of Andrew Carrier

Key Terms

beneficially owns, Schedule 13D, Framework Agreement, LLC Agreement, +1 more

5 terms

beneficially owns financial

"MSI beneficially owns 58,780,450 shares of Common Stock, representing fifteen and eight-tenths percent"

Beneficially owns means a person or entity enjoys the economic benefits and control of a security even if the legal title or registration is held in another name. Think of it like having the keys and profits from a car that is registered to a friend: you use it, benefit from it, and make decisions about it even though the official paperwork lists someone else. For investors, this matters because it reveals who truly controls shares, affects voting power, potential conflicts of interest, and regulatory disclosure obligations.

Schedule 13D regulatory

"This Amendment No. 4 amends the Statement on initially filed on December 11, 2025"

A Schedule 13D is a legal document that investors file with regulators when they buy a large enough stake in a company to potentially influence its management or decisions. It provides details about the investor’s intention, ownership stake, and plans, helping other investors understand who is gaining control and what their motives might be.

Framework Agreement financial

"Mr. Carrier was designated by MSI pursuant to the terms of the Framework Agreement."

A framework agreement is a standing contract that lays out general rules, pricing ranges, and how the parties will work together when they later sign specific orders or projects — like an umbrella that covers future deals without fixing every detail up front. Investors watch these because they make future revenue more predictable, can speed up repeat business, and may signal the scale or stability of upcoming sales, reducing uncertainty about a company’s growth.

LLC Agreement financial

"As a result of the Framework Agreement and LLC Agreement described in Item 6 of this Statement"

kabushiki kaisha financial

"a kabushiki kaisha (stock corporation) organized under the laws of Japan"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How large is Mitsui Sumitomo Insurance’s stake in W. R. Berkley (WRB)?

Mitsui Sumitomo Insurance beneficially owns 58,780,450 shares of W. R. Berkley common stock, representing 15.8% of shares outstanding as of April 27, 2026. This ownership level reflects a significant strategic position in the insurer’s equity base.

What additional W. R. Berkley (WRB) shares are linked through Family Holdings?

The filing states that WR Berkley & Others LLC (Family Holdings) beneficially owns 63,515,547 W. R. Berkley shares, about 17.1% of outstanding stock. Due to a Framework Agreement and an LLC Agreement, the reporting persons may be deemed to share voting power over these shares.

Did MS&AD Insurance Group Holdings change its beneficial ownership in WRB?

MS&AD Insurance Group Holdings may be deemed an indirect beneficial owner of the 58,780,450 shares held by Mitsui Sumitomo Insurance because MSI is its wholly owned subsidiary. However, MS&AD explicitly disclaims beneficial ownership of those W. R. Berkley shares in the amendment.

What governance rights did Mitsui Sumitomo gain at W. R. Berkley (WRB)?

In connection with acquiring 15% of the Outstanding Agreement Shares, Mitsui Sumitomo Insurance designated executive Andrew Carrier to W. R. Berkley’s board. He was nominated by the board and elected as a director at the June 3, 2026 annual stockholders’ meeting.

Have Mitsui Sumitomo or MS&AD traded W. R. Berkley (WRB) shares recently?

The reporting persons state that neither they nor, to their knowledge, any person named in Item 2 has effected any transactions in W. R. Berkley common stock during the past 60 days, indicating no recent trading activity disclosed in this amendment.

Do Mitsui Sumitomo, MS&AD, and Family Holdings form a group in WRB stock?

The amendment notes that, because of the Framework Agreement and LLC Agreement, the reporting persons may be deemed to beneficially own shares held by Family Holdings. However, it explicitly states this is not an admission that they constitute a “group” under Rule 13d-5(b)(1).

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 06/04/2026 - 08:36 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 4)

W. R. BERKLEY CORPORATION

(Name of Issuer)

Common Stock, par value $0.20 per share

(Title of Class of Securities)

084423102

(CUSIP Number)

Mitsui Sumitomo Insurance Co.,
Ltd., Attn: Kunihisa Kawasaki, 9, Kanda-Surugadai, 3-chome, Chiyoda-Ku
Tokyo, M0, 101-8011
81-3-3259-1462

Debevoise & Plimpton LLP,
Attn: Eric T. Juergens, Esq, 66 Hudson Boulevard
New York, NY, 10001
(212) 909-6000

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

06/03/2026

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

schemaVersion:

SCHEDULE 13D

CUSIP Number(s): 084423102

1

Name of reporting person

Mitsui Sumitomo Insurance Co., Ltd.

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

JAPAN

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 58,780,450.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 58,780,450.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

58,780,450.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

15.8 %

14

Type of Reporting Person (See Instructions)

IC

Comment for Type of Reporting Person:

The aggregate amount in row (11) does not reflect shares of common stock, par value $0.20 per share (the "Common Stock"), of W. R. Berkley Corporation (the "Issuer") held by WR Berkley & Others LLC ("Family Holdings"), as further described in Items 5(a) and 6. Percentages are based on 372,276,732 shares of Common Stock outstanding as of April 27, 2026, as reported in the Issuer's Form 10-Q filed with the Securities and Exchange Commission on May 1, 2026.

SCHEDULE 13D

CUSIP Number(s): 084423102

1

Name of reporting person

MS&AD Insurance Group Holdings, Inc.

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

JAPAN

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 58,780,450.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 58,780,450.00

11

Aggregate amount beneficially owned by each reporting person

58,780,450.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

15.8 %

14

Type of Reporting Person (See Instructions)

HC

Comment for Type of Reporting Person:

The aggregate amount in row (11) does not reflect shares of Common Stock held by Family Holdings, as further described in Items 5(a) and 6. Percentages are based on 372,276,732 shares of Common Stock outstanding as of April 27, 2026, as reported in the Issuer's Form 10-Q filed with the Securities and Exchange Commission on May 1, 2026.

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common Stock, par value $0.20 per share
(b)	Name of Issuer: W. R. BERKLEY CORPORATION
(c)	Address of Issuer's Principal Executive Offices: 475 STEAMBOAT ROAD, GREENWICH, CONNECTICUT , 06830.
Item 1 Comment: This Amendment No. 4 amends the Statement on Schedule 13D initially filed on December 11, 2025 with the Securities and Exchange Commission, and amended on January 14, 2026, February 6, 2026 and March 5, 2026 (as amended, the "Statement") by MS&AD Insurance Group Holdings, Inc., a kabushiki kaisha (stock corporation) organized under the laws of Japan ("MS&AD Holdings"), and Mitsui Sumitomo Insurance Co., Ltd., a kabushiki kaisha (stock corporation) organized under the laws of Japan ("MSI" and together with MS&AD Holdings, the "Reporting Persons").
Item 2.	Identity and Background
(a)	Item 2 is hereby amended and restated in its entirety to read as follows: The persons filing this Statement are MS&AD Insurance Group Holdings, Inc., a kabushiki kaisha (stock corporation) organized under the laws of Japan, and Mitsui Sumitomo Insurance Co., Ltd., a kabushiki kaisha (stock corporation) organized under the laws of Japan. MS&AD Holdings is an insurance holding company, the shares of which are listed on the Tokyo Stock Exchange and Nagoya Stock Exchange. MSI is an insurance company and a wholly-owned subsidiary of MS&AD Holdings.
(b)	The principal business address of MS&AD Holdings is Tokyo Sumitomo Twin Building (West Tower), 27-2, Shinkawa 2-chome, Chuo-ku, Tokyo, Japan. The principal business address of MSI is 9, Kanda-Surugadai 3-chome, Chiyoda-Ku, Tokyo, Japan.
(c)	Schedule A to this Statement includes the name, business address, present principal occupation or employment and citizenship of the directors and executive officers of each of the Reporting Persons and is incorporated herein by reference.
(d)	During the last five years, neither of the Reporting Persons nor any of their respective directors or executive officers identified in Schedule A to this Statement has been convicted in a criminal proceeding (excluding traffic violations and similar misdemeanors).
(e)	During the last five years, neither of the Reporting Persons nor any of their respective directors or executive officers identified in Schedule A to this Statement was a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.
(f)	MS&AD Holdings and MSI are organized under the laws of Japan.
Item 4.	Purpose of Transaction
	Item 4 is hereby amended by replacing the second to last paragraph of Item 4 with the following: In connection with MSI's acquisition of fifteen percent (15%) of the Outstanding Agreement Shares, MSI designated Andrew Carrier, an executive officer of MSI, to serve as a director of the Issuer. Mr. Carrier was nominated to the slate of directors up for election to the Issuer's Board at the Issuer's 2026 annual meeting by the Issuer's Board following the recommendation of the Issuer's Nominating and Corporate Governance Committee to the Board. On June 3, 2026, Mr. Carrier was elected to the Board at the annual meeting of stockholders of the Issuer. Mr. Carrier was designated by MSI pursuant to the terms of the Framework Agreement.
Item 5.	Interest in Securities of the Issuer
(a)	Item 5 is hereby amended and restated in its entirety to read as follows: MSI beneficially owns 58,780,450 shares of Common Stock, representing fifteen and eight-tenths percent (15.8%) of the shares of Common Stock outstanding. Because MSI is its wholly-owned subsidiary, MS&AD Holdings may, in accordance with the rules of the Securities and Exchange Commission, be deemed to be an indirect beneficial owner of the shares of Common Stock beneficially owned by MSI. MS&AD Holdings disclaims beneficial ownership of such shares. The percentage beneficial ownership of the Reporting Persons has been determined based on 372,276,732 shares of Common Stock outstanding as of April 27, 2026, as reported in the Issuer's Form 10-Q filed with the Securities and Exchange Commission on May 1, 2026. The beneficial ownership information set forth above does not include any securities of the Issuer beneficially owned by Family Holdings. As a result of the Framework Agreement and LLC Agreement described in Item 6 of this Statement, the Reporting Persons may be deemed to beneficially own and share voting power over the shares of Common Stock beneficially owned by Family Holdings. As of March 5, 2026, Family Holdings beneficially owns an aggregate of 63,515,547 shares of Common Stock (approximately seventeen and one-tenth percent (17.1%) of the total number of shares of Common Stock outstanding). This Statement is not an admission or acknowledgment that the Reporting Persons constitute a "group" within the meaning of Rule 13d-5(b)(1) under the Act with Family Holdings.
(b)	In addition to the description set forth above in Item 5(a), see the cover pages of this Statement for indications of the respective voting powers and disposition powers of the Reporting Persons.
(c)	Each of the Reporting Persons reports that neither it, nor to its knowledge, any other person named in Item 2 of this Statement, has effected any transactions in Common Stock during the past 60 days.
(d)	Except as set forth herein, no one other than the Reporting Persons has the right to receive, or the power to direct the receipt of, dividends from, or the proceeds from the sale of, any of the securities of the Issuer beneficially owned by the Reporting Persons as described in this Item 5.
(e)	Not applicable.
Item 7.	Material to be Filed as Exhibits.
	99.14 Joint Filing Agreement, dated December 11, 2025, by and between Mitsui Sumitomo Insurance Co., Ltd. and MS&AD Insurance Group Holdings, Inc. (incorporated by reference to Exhibit 99.1 to the Schedule 13D filed by the Reporting Persons with the SEC on December 11, 2025) 99.15 Schedule A, dated June 4, 2026

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Mitsui Sumitomo Insurance Co., Ltd.

Signature:	/s/ Hironori Morimoto
Name/Title:	Hironori Morimoto/Authorized Signatory
Date:	06/04/2026

MS&AD Insurance Group Holdings, Inc.

Signature:	/s/ Hironori Morimoto
Name/Title:	Hironori Morimoto/Authorized Signatory
Date:	06/04/2026