Do not know of any Martins in this Davidson branch, but my knowledge of the family is extremely limited. It is unlikely that my Ellen Davidson would be mother to John Martin who married in 1917 since she herself was born ~ 1832 and would have been 85 at the time of the wedding - unless a brother to Ellen may have had a daughter with the same name. My Ellen's supposed brother Thomas Davidson.
Ellen's suspected brother, Thoimas, had three sons, born in Ireland, Alexander 1851, Thomas 1853, John 1857 and James 1859. I know that Thomas b. 1853 had a son James ~ 1896 probably born in Scotland; there may have been other children born to him. I do not as yet have information on the marriages and descendants of the remaining brothers, but am keen to discover more.