Cynegils was the grandson of Cutha. He was the son of Ceol of Wessex and probably the nephew of Ceolwulf. He ruled jointly with his son Cwichelm. The Anglo-Saxon Chronicle for the year 614 says Cynegils and Cwichelm fought together at a place named Beandun. The account said they slew two thousand sixty-five Welsh. This was a major victory for the West Saxons. Cynegils had some however during the middle of his reign. His son Cwichelm sent someone to try to kill King Edwin of Northumbria. When Edwin attacked Wessex in five Kings of Wessex were killed. The Northumbrian attack weakened the West Saxon army. The Anglo-Saxon Chronicle for 628 says that Cyngils, king of Wessex, and Cwichelm his son 'fought with Penda at Cirencester and came to an agreement with him there'. The 'agreement' seems to have been to give Cirencester to Penda. So this was a defeat for Cynegils and his son Cwichelm and a permanent loss of Cirencester.