Thomas and Bartholomew were brothers. Bartholomew's wife, Grace Denny and Thomas' wife Eleanor arrived in New York together, along with their children, on 8/17/1844 aboard the Olive. I could not find the men coming to America, but I would assume they came sometime before their families. They are also found in the 1860, 1870, and 1880 censuses but the spellings are really botched up (1860 Bartholomew Satlen, Thomas Lochlin, 1870 Bartholomew Saughlin, 1880 Barthole Laughlin).
I believe* their parents were Thomas Lockman and Anne Musgrave, married in Cape Breton in 1800/01. They had other brothers Richard, who never left Cape Breton and I believe Lockmans currently living there are descended from him, John, Patrick, and Peter Thomas. Peter came to WV and I think had some involvement in the Civil War but have not really looked into that much, Patrick died in Quebec, and John also seems to have stayed in Cape Breton.
* I have only been able to confirm Richard as son of Thomas and Anne but Irish naming conventions were pretty rigid at the time - oldest son (Richard) named after paterneral grandfather, second son (Bartholomew) named after materernal grandfather (Anne's father was Bartholomew Musgrave**), 3rd son (Thomas) named after father. The only other Lockman/Loughlin/Laughlin identified in Cape Breton at the time was a German doctor named Leonard and he only had a daughter who never married or had children. Also my DNA test showed a match with someone named John Musgrave. So I don't have a paper trail, but I'm fairly confident in the link.
** Very interesting Loyalist history, easy to Google.
Bartholomew was my 3rd GGF.