Nielsen Hayden genealogy
Descendants of Madog ab Iorwerth ap Madog ap Gruffudd
Madog ab Iorwerth ap Madog ap Gruffudd
   └─ Gwerfyl ferch Madog (of Hendwr in Edeirnion, Merionethshire, Wales - Aft 1293)
    Gronwy ap Tydyr HĂȘn ap Gronwy (of Penmynydd, Anglesey, Wales - 1331 bur.Bangor, Gwynedd, Wales)
       └─ Tudur ap Gronwy ( - 1367 Trecasteil, Anglesey, Wales)
        Margred ferch Thomas (of Iscoed, Ceredigion, Wales - ??)
            + Margred ferch Dafydd Vychan (of Trefeilir in Malltraeth, Anglesey, Wales - ??)