Gruffydd was the eldest son of Rhys ap Gruffydd by his wife Gwenllian, daughter of Madog ap Maredudd prince of Powys.
Madog's intervention in the Battle of Lincoln in 1141 forms an important plot element in the detective novel Dead Man's Ransom, part of the Brother Cadfael chronicles by Edith Pargeter (writing as Ellis Peters).
Maelgwn was the son of Rhys ap Gruffydd (The Lord Rhys) by his wife Gwenllian ferch Madog, daughter of Madog ap Maredudd prince of Powys.
Rhys was the fourth son of Rhys ap Gruffydd (The Lord Rhys) and his wife Gwenllian, daughter of Madog ap Maredudd of Powys.
Madog ap Maredudd | Maredudd ab Owain | Morgan ap Maredudd | Maredudd ap Cynan ab Owain Gwynedd | Madog II ap Gruffydd, Lord of Dinas Bran | Madog ap Llywelyn | Madog ap Gruffydd Maelor | Llywelyn the Elder ap Maredudd ap Cynan ab Owain Gwynedd | John "Wynn" ap Maredudd | Gruffydd II ap Madog, Lord of Dinas Bran |
It is from the youngest of these sons, Iorwerth ab Owain ap Madog ap Maredudd, that the barons of Cymmer yn Edeyrnion claim descent.