"...Nor do we have any early authority which cites [Cadell's] marriage; modern writers call her Rheingar but give her no ancestry. By tradition, she supposedly was a lady of Dinefwr in Ystrad Tywy.
Subsequent events lead us to identify this lady as probably a sister of Llywarch and Rhodri ap Hyfaidd ap Bleddri; that family had replaced the ruling Dyfed family when it became extinct in the male line...." 1
Marriage Information:
Rheingar married Cadell ap Rhodri, King of Deheubarth, son of Rhodri "Mawr" (The Great) ap Merfyn and Angharad ferch Meurig. (Cadell ap Rhodri was born in 861 in Deheubarth, Wales and died in 909.)