The family of Walter Stapeldon can be traced back no further than a single generation. The names of his parents, William and Mabel, may be gleaned from an entry in his register. It may be that his father took the name Stapeldon on migrating to the district. There is certainly no evidence of the noble ancestry which one eighteenthcentury antiquarian attributed to the bishop. His father was probably a prosperous freeholder but is never designated a knight: and there are no other references to his mother.

His father has to be distinguished from two other William Stapeldons probably of Stapeldon in the hundred of Braunton in north Devon. The bishop's family home was at Stapeldon near Cookbury in the hundred of Black Torrington in north-west Devon. There is clear evidence that his brother Richard owned the manor and resided there. Once this is recognised the bishop's father may be identified by the geographical location of land in deeds which bear his name. A number of such deeds have been found amongst the muniments of Wardour castle. Most of them concern transactions between Robert Cnoyl and Oliver Dynham in the hundreds of Black Torrington and Shebbear. In one of these deeds, dated 6 March 1287, Cnoyl appoints William Stapeldon his attorney to seize Dynham of lands in Upcott and Sheepwash.