Maredudd was the son of Owain ab Edwin and was hence the male-line heir of Hywel Dda.
During Maredudd's reign the Normans sacked south-east Wales in response to Welsh support for Saxon revolts like that of Eadric the Wild.
After a few attempts to halt this, Maredudd decided not to resist the Norman encroachment on Gwent and was rewarded with lands in England in 1070.
He was succeeded by his brother, Rhys ab Owain, rather than his young son, Gruffydd ap Maredudd.
When Rhys ab Owain died, the realm was seized by Rhys ap Tewdwr (Maredudd's second cousin, descended from a younger son of Einion).