 Arthur Forbes was a son of William Forbes of Corsse, by his wife Elizabeth Strachan, a daughter of the Laird of Thornton.Forbes was directly descended from the Patrick Forbes of Corsse, a younger son of James Forbes, 2nd Lord Forbes (died 1476) and his spouse, Egidia, daughter of William Keith, Earl-Marischal of Scotland.He settled in Ireland in 1620, and was made by Letters Patent, dated at Dublin, in 1622, a free denizen of that kingdom.