White Mountains Insurance Group, Ltd. WTM NYSE

NYSE • Financial Services • Insurance - Property & Casualty • BM • USD

White Mountains Insurance Group, Ltd. (WTM) has 20 known insider and institutional holders on record. The largest holder is BERKSHIRE HATHAWAY INC with 89,279 shares. Other notable holders include SEELIG ROBERT LAWRENCE and Rountree George Manning.

Over the last 12 months, insiders have made 28 transactions in WTM stock — 14 buys (valued at RSU Award) and 4 sells (valued at $20.84M). Insider buying has outpaced selling during this period, which may signal confidence in the company's prospects.

WTM Insider Ownership

Top Holder

BERKSHIRE HATHAWAY INC

89,279 shares

Buys (12 mo)

$0.00 value

Sells (12 mo)

$20.84M value

12-Month Transaction Activity

Buy 50%

Sell 14%

Top Insider Holders

#	Name	Role	Shares Owned	Last Filed	Relative Size
1	Berkshire Hathaway Inc	10 Percent Owner	89,279	2008-11-03	100%
2	Seelig Robert Lawrence	EVP & General Counsel	17,857	2026-03-20	20%
3	Rountree George Manning	Chief Executive Officer	13,809	2025-12-22	15%
4	Campbell Reid Tarlton	Director	10,440	2025-12-22	12%
5	Barrette Raymond Joseph Rene	Chief Executive Officer	9,000	2017-01-19	10%
6	Foy David Thomas	Chief Financial Officer	8,900	2016-08-25	10%
7	Cochran Robert Phillips	Director	8,045	2011-05-31	9%
8	Davis Morgan W	Director	6,709	2022-12-29	8%
9	Fass Steve Elliott	Director	5,535	2007-02-27	6%
10	Linker David	Chief Investment Officer	4,725	2017-03-03	5%
11	Brouillette Yves	Director	4,121	2019-05-28	5%
12	Waters Allan Lewis	CEO - Sirius Int'l Ins. Group	3,735	2015-02-27	4%
13	Caffrey Liam P	Chief Executive Officer	3,650	2026-02-27	4%
14	Bazos Frank R	EVP and Head of M&a	3,600	2020-03-02	4%
15	Holiday Edith E	Director	2,827	2020-05-22	3%
16	Hicks Weston M	Director	2,746	2025-05-23	3%
17	Harrison Giles E	President	2,675	2026-02-27	3%
18	Oberting Kernan V	Managing Director	2,134	2016-01-05	2%
19	Tanner David Allen	Director	1,879	2026-03-05	2%
20	Choksi Mary C	Director	1,858	2025-05-23	2%

Recent Transactions (last 12 months)

Date	Name	Role	Type	Shares	Price	Value
2026-03-19	Seelig Robert Lawrence	EVP & General Counsel	Gift (Given)	50	-	-
2026-03-04	Tanner David Allen	Director	Gift (Given)	225	-	-
2026-02-25	Papamichael Michael A	Chief Financial Officer	RSU Award	500	-	-
2026-02-25	Harrison Giles E	President	RSU Award	775	-	-
2026-02-25	Caffrey Liam P	Chief Executive Officer	RSU Award	1,500	-	-
2026-02-25	Hildreth Michaela	Md & Chief Accounting Officer	RSU Award	600	-	-
2026-02-25	Seelig Robert Lawrence	EVP & General Counsel	RSU Award	775	-	-
2026-01-01	Hildreth Michaela	Md & Chief Accounting Officer	Tax Withholding of RSU	274	$2,078.03	$569.38K
2026-01-01	Papamichael Michael A	Chief Financial Officer	Tax Withholding of RSU	131	$2,078.03	$272.22K
2026-01-01	Papamichael Michael A	Chief Financial Officer	Unknown	-	-	-
2026-01-01	Caffrey Liam P	Chief Executive Officer	Tax Withholding of RSU	425	$2,078.03	$883.16K
2026-01-01	Seelig Robert Lawrence	EVP & General Counsel	Tax Withholding of RSU	398	$2,078.03	$827.06K
2025-12-23	Hildreth Michaela	Md & Chief Accounting Officer	Gift (Given)	60	-	-
2025-12-19	Rountree George Manning	Chief Executive Officer	Informative Sell	5,000	$2,050.00	$10.25M
2025-12-19	Campbell Reid Tarlton	Director	Informative Sell	5,000	$2,050.00	$10.25M
2025-12-19	Campbell Reid Tarlton	Director	Informative Sell	5,000	-	-
2025-12-16	Gelston Philip A	Director	Informative Sell	165	$2,048.51	$338K
2025-11-25	Campbell Reid Tarlton	Director	Gift (Given)	50	-	-
2025-11-10	Tanner David Allen	Director	Gift (Given)	4	-	-
2025-05-22	Shank Suzanne F.	Director	RSU Award	150	-	-
2025-05-22	Yi Steven	Director	RSU Award	150	-	-
2025-05-22	Dillon Margaret	Director	RSU Award	150	-	-
2025-05-22	Gelston Philip A	Director	RSU Award	150	-	-
2025-05-22	Carlson Peter M	Director	RSU Award	150	-	-
2025-05-22	Campbell Reid Tarlton	Director	RSU Award	150	-	-