Neuberger Berman reports 121,583 shares (4.9%) of White Mountains

Neuberger Berman Group LLC and related advisers reported beneficial ownership of 121,583 shares of White Mountains Insurance Group common stock, representing 4.9% of the class.

Rhea-AI Filing Summary

Neuberger Berman Group LLC and related advisers reported beneficial ownership of 121,583 shares of White Mountains Insurance Group common stock, representing 4.9% of the class. The filing attributes 110,283 shared voting power and 121,583 shared dispositive power to the reporting group.

The filing describes multiple Neuberger Berman affiliates and fiduciary capacities, notes information barriers that exclude certain subsidiaries, and includes standard disclaimers under Exchange Act Rules 13d-3 and 13d-4.

Insights

Securities Compliance Attorney

Routine Schedule 13G/A filing reporting sub-5% institutional holdings.

This amendment documents beneficial ownership of 121,583 shares and 4.9% of the class, with shared voting/dispositive power allocated among named Neuberger Berman entities. The text includes fiduciary disclaimers and information-barrier carve-outs.

Impact is procedural: ownership is below the 5% threshold that typically triggers Schedule 13D treatment, so this remains an informational disclosure rather than an activist or control signal.

Key Figures

Beneficial ownership: 121,583 shares Percent of class: 4.9% Shared voting power: 110,283 shares +1 more

4 metrics

Beneficial ownership 121,583 shares reported beneficially owned

Percent of class 4.9% percent of class reported

Shared voting power 110,283 shares shared power to vote or to direct the vote

Shared dispositive power 121,583 shares shared power to dispose or to direct the disposition

Key Terms

Schedule 13G/A, beneficially own, information barrier, Exchange Act Rule 13d-4

4 terms

Schedule 13G/A regulatory

"This amendment documents beneficial ownership under Schedule 13G/A"

A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.

beneficially own regulatory

"may be deemed to beneficially own the securities covered by this report"

Beneficially own means having the economic rights and risks of a security—such as the right to receive dividends, sell the shares, or profit from price changes—whether or not your name appears on the official share register. Think of it like renting a car: you use it and reap the benefits even if the title lists someone else. Investors care because beneficial ownership determines who truly controls value, must be disclosed under securities rules, and can signal potential influence or trading activity that affects a stock’s price.

information barrier regulatory

"separated from the NBG Filers by an information barrier"

Exchange Act Rule 13d-4 regulatory

"disclaim beneficial ownership of the securities covered by this statement pursuant to Exchange Act Rule 13d-4"

FAQ

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

What stake did Neuberger Berman report in White Mountains (WTM)?

They reported beneficial ownership of 121,583 shares, representing 4.9% of the class. The report lists shared voting power of 110,283 and shared dispositive power of 121,583 among affiliated Neuberger Berman entities.

Does this Schedule 13G/A signal a change in control of WTM?

No; this filing reports ownership below the 5% threshold and contains fiduciary disclaimers. The filing characterizes the position as passive and includes information‑barrier language that excludes certain Neuberger Berman subsidiaries from the reported total.

Which Neuberger Berman entities are named as reporting holders?

The filing names Neuberger Berman Group LLC and Neuberger Berman Investment Advisers LLC, plus related trust and affiliate entities. It explains control relationships and fiduciary roles under Exchange Act Rules 13d-3 and 13d-4.

How does shared voting or dispositive power appear in this filing?

The report shows 0 sole voting/dispositive power and records 110,283 shared voting power and 121,583 shared dispositive power. Those figures reflect the aggregate holdings attributed to the reporting group.

When was the Schedule 13G/A signed and certified?

The filing is signed by Brad Cetron, Managing Director, with signature dates shown as 05/07/2026. The cover indicates an amendment dated 04/30/2026 for the reported ownership information.

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

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Accepted by SEC EDGAR 05/07/2026 - 11:56 AM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

WHITE MOUNTAINS INSURANCE GROUP LT

(Name of Issuer)

COMMON

(Title of Class of Securities)

G9618E107

(CUSIP Number)

04/30/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): G9618E107

1

Names of Reporting Persons

Neuberger Berman Group LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 110,283.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 121,583.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

121,583.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

4.9 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

CUSIP Number(s): G9618E107

1

Names of Reporting Persons

Neuberger Berman Investment Advisers LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 106,687.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 117,789.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

117,789.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

4.8 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

Item 1.
(a)	Name of issuer: WHITE MOUNTAINS INSURANCE GROUP LT
(b)	Address of issuer's principal executive offices: 23 SOUTH MAIN STREET, SUITE 3B, hanover, NH, 03755.
Item 2.
(a)	Name of person filing: Neuberger Berman Group LLC Neuberger Berman Investment Advisers LLC
(b)	Address or principal business office or, if none, residence: 1290 Avenue of the Americas New York, NY 10104
(c)	Citizenship: Delaware
(d)	Title of class of securities: COMMON
(e)	CUSIP No.: G9618E107
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 121,583 Neuberger Berman Trust Co N.A., Neuberger Berman Trust Co of Delaware N.A., Neuberger Berman Asia Ltd., Neuberger Berman Canada ULC, and Neuberger Berman Investment Advisers LLC and certain affiliated persons may be deemed to beneficially own the securities covered by this report in their various fiduciary capacities by virtue of the provisions of Exchange Act Rule 13d-3. Neuberger Berman Group LLC, through its subsidiaries Neuberger Berman Investment Advisers Holdings LLC and Neuberger Trust Holdings LLC controls Neuberger Berman Trust Co N.A., Neuberger Berman Asia Ltd., Neuberger Berman Canada ULC, Neuberger Berman Trust Co of Delaware N.A. and Neuberger Berman Investment Advisers LLC and certain affiliated persons. This report is not an admission that any of these entities are the beneficial owner of the securities covered by this report and each of Neuberger Berman Group LLC, Neuberger Berman Investment Advisers Holdings LLC, Neuberger Trust Holdings LLC, Neuberger Berman Trust Co N.A., Neuberger Berman Asia Ltd., Neuberger Berman Canada ULC, Neuberger Berman Trust Co of Delaware N.A. and Neuberger Berman Investment Advisers LLC and certain affiliated persons disclaim beneficial ownership of the securities covered by this statement pursuant to Exchange Act Rule 13d-4. The information in this filing reports securities of the issuer that may be deemed to be beneficially owned by Neuberger Berman Group LLC, Neuberger Berman Investment Advisers Holdings LLC, Neuberger Trust Holdings LLC, Neuberger Berman Trust Co N.A., Neuberger Berman Asia Ltd., Neuberger Berman Canada ULC, Neuberger Berman Trust Co of Delaware N.A. and Neuberger Berman Investment Advisers LLC ("NBG Filers"). The securities of the issuer, if any, that may be deemed to be beneficially owned by NB Alternatives Advisers LLC and other subsidiaries of Neuberger Berman Group LLC that are separated from the NBG Filers by an information barrier in accordance with SEC Release No. 34-39538 (January 12, 1998) are not reflected in this filing.
(b)	Percent of class: 4.9 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 0
	(ii) Shared power to vote or to direct the vote: 110,283
	(iii) Sole power to dispose or to direct the disposition of: 0
	(iv) Shared power to dispose or to direct the disposition of: 121,583
Item 5.	Ownership of 5 Percent or Less of a Class.
	Ownership of 5 percent or less of a class
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

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.

Neuberger Berman Group LLC

Signature:	Brad Cetron
Name/Title:	Brad Cetron / Managing Director
Date:	05/07/2026

Neuberger Berman Investment Advisers LLC

Signature:	Brad Cetron
Name/Title:	Brad Cetron / Managing Director
Date:	05/07/2026