Budic II was born in Cornouaille to a member of its royal family, either
Cybydan. He was named after his uncle Budic I. He succeeded to the throne c. 478 but was expelled by a cousin and fled to the court of King Aircol Lawhir of Dyfed, where another cousin
Amon Ddu was employed. There, he wed Anowed or Arianwedd, the daughter of Saint Issel and the sister of Saint Teilo. After the death of his usurping relative, he returned to Cornouaille to claim the Breton throne, later joined by Saint Teilo whom he reputedly persuaded to rid the area of a terrible dragon that had been terrorising the countryside. Teilo was able to subdue the beast and tied it to a rock in the sea. Some sources claim he died in 545. However, this contradicts other sources which claim that Saint Teilo had fled to France in 549 to escape the Yellow Plague of Rhos and had spent time in Brittany in Budic's company.