Sources disagree on the name of the mother of Gruffydd, some say it is Gwenllian.

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Father: ap Owain Gwynedd, Iorwerth Drwyndwn
Mother: , Margaret
Married to , Gwenllian

Married to , Joan of England
Child 1: ap Llywelyn Fawr, Dafydd, Prince of Gwynedd
Child 2: , Elen (Helena)
Child 3: , Angharad
Child 4: verch Llywelyn, Margaret
Child 5: Wen, Tegwared-y-Bais
Associated with Goch, Tangwystyl
Child 6: ap Llywelyn Fawr, Gruffydd
Child 7: , Gwladus DDU "the Dark"
Child 8: , Helen