Gwenllian verch Ednyfed Fychan of Brynffenigl

Gwenllian's father was Ednyfed Fychan ap Kendrig Lord Brynffenigl and her mother was Tangwystl Goch verch Llywarch of Rhos. She had six brothers and a sister, named Howel ap Ednyfed Fychan, Sir Tudor, Kendrig, Llewelyn, Rhys, Iorwerth ap Ednyfed Fychan and Angharad. She had a half-brother and two half-sisters, named Gruffydd ap Llywelyn Fawr, Gwladus Ddu "the Dark and Gwenllian.

‌Gwenllian and Llywelyn Fawr ap Iorwerth were married in a religious ceremony.