About Margaret verch Dafydd
Please see Darrell Wolcott: The Welsh Ancestry of the Tudor Dynasty; http://www.ancientwalesstudies.org/id217.html. (Steven Ferry, July8, 2017.)
Tudur and Margaret were parents to Maredudd ap Tudur (d. 1406); Maredudd married Margaret ferch Dafydd. (Margaret was daughter to Dafydd Fychan, Lord of Anglesey and his wife Nest ferch Ieuan.)
Maredudd ap Tudur and Margaret ferch Dafydd were the parents to Owen Tudor.