According to early modern genealogist Lewys Dwnn, Dafydd ap Dafydd ap Llywelyn was the illegitimate son of Dafydd ap Llywelyn, Prince of Wales and King of Gwynedd between 1240–1246. He is considered the ancestor of the Prys or Price of Esgairweddan family, who bore the royal arms of Gwynedd as their own. It is generally considered that this family, in the male line, died out on the death of Robert Price of Esgairweddan in 1702.