The only KILMARTIN in my tree that I am 100% sure of came from Ireland was my great great grandfather Daniel, who was likely born Abt. 1820 in Ireland, specifically where, I do not know. So I cannot suggest a link at this time.
His father was also Daniel, and his mother was CATHERINE LADEN. He married ELEANORA (HELEN) CARTY in Ireland, likely around 1844, having at least one child there, Michael, born Abt. 1845, Drumcliff & Magherow, and their subsequent children, including my great grandfather Daniel were all likely born in Glasgow.
I have no knowledge of the fate of any of my great grandfather's siblings either.
Family lore has always indicated Sligo as the family's place of origin, and the LDS indicates the baptism of MICHAEL KILMARTEN in 1845, as indicated above, parents being the same names as my ancestors, so I'm confident that he was their 1st child.
I wish I knew more, and would appreciate any of those wonderful people out there who might be able to provide assistance for folk like you and I to trace our roots.
NEIL in CANADA