Maelgwn was described as being short in stature and a turbulent character, who caused his father much trouble in his later years and maintained a lengthy feud with his brother Gruffydd.
When Gwenwynwyn was defeated at Painscastle by Norman forces in 1198 Gruffydd was set free and recaptured all Ceredigion from Maelgwn except for the castles of Cardigan and Ystrad Meurig.
The annalist of Brut y Tywysogion commented: Gruffydd died in 1201, enabling Maelgwn to seize Cilgerran Castle, but in 1204 he lost it to William Marshall.
In 1205 according to Brut y Tywysogion, Maelgwn caused a certain Irishman to kill Cedifor ap Gruffudd and his four sons with a battle-axe after they had been captured.
However, when Llywelyn held a parliament at Aberdyfi in 1216, at which he redistributed the lands formerly under the rule of the Lord Rhys, Maelgwn was still only allowed the southern part of Ceredigion.