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TCGX Acquisition Corp. II (TCXB) is the subject of an ownership disclosure naming Third Rock Ventures VI, L.P. as the direct holder of 990,000 Class A ordinary shares, approximately 9.5% of the class. Its general partner, Third Rock Ventures GP VI, L.P., and that partnership’s general partner, TRV GP VI, LLC, may each be deemed beneficial owners of the same shares; all three report shared voting and dispositive power over 990,000 shares, with zero sole voting or dispositive power. The percentage is based on 10,450,000 Class A ordinary shares outstanding following the issuer’s initial public offering and concurrent private placement on October 19, 2026. The three entities disclaim the existence of a group for purposes of Rule 13d-5.
Key Figures
Class A ordinary shares directly owned:990,000 sharesOwnership of Class A ordinary shares:Approximately 9.5%Class A ordinary shares outstanding:10,450,000 shares
3 metrics
Class A ordinary shares directly owned990,000 sharesHeld directly by Third Rock Ventures VI, L.P.
Ownership of Class A ordinary sharesApproximately 9.5%Reported by the three Third Rock entities
Class A ordinary shares outstanding10,450,000 sharesFollowing the initial public offering and concurrent private placement on October 19, 2026
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.
shared voting powerregulatory
"Shared Voting Power 990,000.00"
Shared voting power occurs when two or more parties jointly have the right to vote or decide how a block of company shares is cast, like co-owners who must agree before moving a piece of furniture. Investors care because who controls voting rights affects board elections, major corporate decisions and takeover outcomes, and shared control can alter regulatory disclosures and the practical influence any holder has over a company’s direction and value.
shared dispositive powerregulatory
"Shared Dispositive Power 990,000.00"
Rule 13d-5regulatory
"disclaim the existence of a "group" for purposes of Rule 13d-5"
FAQ
AI-generated questions and answers. How Rhea-AI works. Not financial advice.
How many TCXB shares does Third Rock Ventures VI own?
Third Rock Ventures VI, L.P. directly owns 990,000 Class A ordinary shares of TCGX Acquisition Corp. II. Its general partner and that partnership’s general partner may also be deemed beneficial owners of the same shares.
How was the 9.5% TCXB ownership figure calculated?
The approximately 9.5% figure is based on 10,450,000 Class A ordinary shares outstanding following the initial public offering and concurrent private placement on October 19, 2026.
Do the Third Rock entities report as a group?
Third Rock Ventures VI, L.P., Third Rock Ventures GP VI, L.P., and TRV GP VI, LLC each disclaim the existence of a group for purposes of Rule 13d-5 and state that the report is not an admission that a group exists or may exist.
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
TCGX Acquisition Corp. II
(Name of Issuer)
Class A ordinary shares, par value $0.0001 per share
(Title of Class of Securities)
G87082106
(CUSIP Number)
10/19/2026
(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):
G87082106
1
Names of Reporting Persons
Third Rock Ventures VI, L.P.
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
990,000.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
990,000.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
990,000.00
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)
9.5 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP Number(s):
G87082106
1
Names of Reporting Persons
Third Rock Ventures GP VI, L.P.
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
990,000.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
990,000.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
990,000.00
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)
9.5 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP Number(s):
G87082106
1
Names of Reporting Persons
TRV GP VI, 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
990,000.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
990,000.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
990,000.00
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)
9.5 %
12
Type of Reporting Person (See Instructions)
OO
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
TCGX Acquisition Corp. II
(b)
Address of issuer's principal executive offices:
245 Lytton Ave., Suite 350, Palo Alto, CA 94301
Item 2.
(a)
Name of person filing:
(i) Third Rock Ventures VI, L.P. ("TRV VI");
(ii) Third Rock Ventures GP VI, L.P. ("TRV GP VI"), which is the sole general partner of TRV VI; and
(iii) TRV GP VI, LLC ("TRV GP VI LLC"), which is the sole general partner of TRV GP VI.
(b)
Address or principal business office or, if none, residence:
The address of the principal business office of each of the Reporting Persons is Third Rock Ventures, LLC, 201 Brookline Ave, Suite 1401, Boston, MA 02215.
(c)
Citizenship:
Each of TRV VI and TRV GP VI is a Delaware limited partnership. TRV GP VI LLC is a Delaware limited liability company.
(d)
Title of class of securities:
Class A ordinary shares, par value $0.0001 per share
(e)
CUSIP Number(s):
G87082106
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:
(i) TRV VI directly owns 990,000 Class A ordinary shares (the "VI Shares").
(ii) TRV GP VI is the general partner of TRV VI and may be deemed to beneficially own the VI Shares.
(iii) TRV GP VI LLC is the general partner of TRV GP VI and may be deemed to beneficially own the VI Shares.
Each of TRV VI, TRV GP VI and TRV GP VI LLC disclaim the existence of a "group" for purposes of Rule 13d-5 of the Securities Exchange Act of 1934, as amended, and nothing contained in this report shall be deemed an admission that any such group exists or may exist.
(b)
Percent of class:
The VI Shares represent approximately 9.5% of the outstanding Class A ordinary shares. The percent of class was based upon 10,450,000 Class A ordinary shares outstanding following the closing of the Issuer's initial public offering and concurrent private placement on October 19, 2026, as disclosed in the Issuer's final prospectus filed with the Securities and Exchange Commission pursuant to Rule 424(b)(4) on October 16, 2026.
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
TRV VI - 0
TRV GP VI - 0
TRV GP VI LLC - 0
(ii) Shared power to vote or to direct the vote:
TRV VI - 990,000
TRV GP VI - 990,000
TRV GP VI LLC - 990,000
(iii) Sole power to dispose or to direct the disposition of:
TRV VI - 0
TRV GP VI - 0
TRV GP VI LLC - 0
(iv) Shared power to dispose or to direct the disposition of:
TRV VI - 990,000
TRV GP VI - 990,000
TRV GP VI LLC - 990,000
Item 5.
Ownership of 5 Percent or Less of a Class.
Not Applicable
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 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.
Third Rock Ventures VI, L.P.
Signature:
/s/ Kevin Gillis
Name/Title:
Kevin Gillis, COO of TRV GP VI, LLC, general partner of Third Rock Ventures GP VI, L.P., general partner of Third Rock Ventures VI, L.P.
Date:
10/26/2026
Third Rock Ventures GP VI, L.P.
Signature:
/s/ Kevin Gillis
Name/Title:
Kevin Gillis, Chief Operating Officer of TRV GP VI, LLC, general partner of Third Rock Ventures GP VI, L.P.
Date:
10/26/2026
TRV GP VI, LLC
Signature:
/s/ Kevin Gillis
Name/Title:
Kevin Gillis, Chief Operating Officer of TRV GP VI, LLC
