Hi Mary,
I think you're on the right track with Robert Weir and Helen Naismith. It looks likely that they are the parents of Helen/Ellen Weir who married your George Craig. Her birth/baptism is missing, but that's not really unusual for the time period.

As for Marion Weir, I think you're heading to the New World for them! A John Wilson, born c. 1844 in Scotland, married an Emma Westbrook on the 27th December 1891 in Algona, Kossuth, Iowa. He gave his parents as Thomas Wilson and Marion Weir.
I think I have found them in the 1860 U.S. census. All b. Scotland except where noted.
Address: Frostburg, Allegany, MarylandThomas Wilson, 35, miner
Marian Wilson, 34
John Wilson, 16, miner
Jannet Wilson, 14
James Wilson, 11
Christena Wilson, 8
Thomas Wilson, 6, b. Maryland
Marian Wilson, 2, b. Maryland
Agnes Wilson, 2 months, b. Maryland
hume
