Einion was the son of Gwallter ap Trahaern but his mother is unknown. The date and place of his birth have not been found.
His wife was Gwerful verch Ieuan Goch. They were married, but the date and place have not been found. Their four known children were NN verch Einion (?-?), Tangwystl verch Einion (?-?), Philip ap Einion (?-?) and Maredudd ap Einion (?-?).