The 13th century History of Gruffydd ap Cynan names "Gwenlliant and Margaret and Rhannillt and Susanna and Annest" as the daughters of Gruffydd ap Cynan by his wife. 1
Marriage Information:
Susanna married Madog "Maelor" ap Maredudd, Tywysog Powys, son of Maredudd ap Bleddyn, Tywysog Powys, and Hunydd ferch Einudd. (Madog ap Maredudd died in 1161 in Winchester, Hampshire, England and was buried in St. Tysilio, Meifod, Montgomeryshire, Wales.)
Sources
1 Foundation for Medieval Genealogy, Medlands: Susann.