Thomas married Matilda Martha Weisend on 8 Mar 1900. Matilda (daughter of Joseph Weisend and Mary Margaret Brister) was born on 2 Feb 1883 in Woodsfield, Monroe County, Ohio, USA; died on 8 Nov 1936 in Toronto, Jefferson County, Ohio, USA. [Group Sheet] [Family Chart]

1. Hugh Harrison O\'Brien was born on 14 Feb 1900.
2. Francis John O\'Brien
3. Margaret O\'Brien
4. Mildred O\'Brien
5. Evelyn Elisabeth O\'Brien
6. Joseph Thomas O\'Brien
7. Dorothy Virginia O\'Brien
8. Mary Lucille O\'Brien
9. Eugene Thomas O\'Brien