Hi Mary,
There are quite a few, aren't there? Weir is quite the popular name in Lanarkshire.

I did have a thought that Marion could be known under her maiden name in 1841, like her mother Helen. So we would be looking for a marriage before 1841.
There is a Marion Weir marrying an Abraham Hamilton in 1840, Hamilton. No children showing on the IGI. Trouble is, they do appear in the 1841 census together. However, it's not the first time someone has been recorded twice on a census! I'm also willing to overlook the Mary/Marion variant too.
Address: Leechlee Street, HamiltonAbraham Hamilton, m, 20, ag. lab., b. in county
Mary Hamilton, f, 20, -, b. in county
More problems follow.

I believe Marion must have died between 1841 and 1846, because there is a marriage between an Abraham Hamilton and a Margaret Forrest in 1846 Hamilton. Here they are in the 1851 census:
Address: Fairholm Gate, HamiltonAbraham Hamilton, head, m, 31, sawier [sic], b. Hamilton
Margret [sic] Hamilton, wife, f, 31, -, b. Blantyre
Helen Hamilton, dau., f, 4, -, b. Hamilton
Ann Hamilton, dau., f, 2, -, b. Hamilton
Thomas Hamilton, son, m, 4 months, -, b. Hamilton
Just all conjecture work, Mary, and nothing at all concrete. It would be nice if there was some clues on the OPR entries though. It's a real nuisance as well there's no pre-1855 death records extant for Hamilton parish either.

hume