Maredudd was the son of Cadwgon I Fantach ap Cadwgon but his mother is unknown. The date and place of his birth have not been found.
His wife was Gwenllian verch Maredudd. They were married, but the date and place have not been found. Their two known children were Ellyw Angharad verch Maredudd (?-?) and Joan verch Maredudd (?-?).