Sources: Young; History of Morgan Family. Young: Cadell of North Wales. History: "Upon the death of his brother, Mervyn-Mawr, Cadell usurped his nephew Llewelyn and seized the Kingdom of Powys. He had a son, Hywel (Howell)." Cadell was the first in the Deheubarth branch of the family. ***** Cadell ap Rhodri Mawr resided at Dynefor. He ruled from about 878 to his death in about 909 or 910. He had other children in addition to Hywel Dda and Clydog.
"Upon the death of his brother, Mervyn-Mawr, Cadell usurped his nephew Llewelyn and seized the Kingdom of Powys. He had a son, Hywel (Howell)." Cadell was the first of the Deheubarth branch of the family. [Source 2]
SOURCES: 1. Bartrum, Peter C. _Welsh Genealogies, AD 300-1400_. University of Wales Press, 1978; page 42. 2. Morgan, Dennis. _A History of the Morgan Family_.