 Robert Boyd was the eldest son of Margaret Chalmers and James Boyd, Archbishop of Glasgow and Chancellor of the University of Glasgow from 1572-1581.He was a great-grandson of Robert Boyd, 1st Lord Boyd and connected to the Cassilis family, later the Marquesses of Ailsa.When Robert was three, his father died and Margaret took him and his brother Thomas to live on an estate in Ayrshire, variously spelled Trochrig, Trochridge, and Trochorege.