Alhfrith was King of Deira under his father, who was King of Bernicia following the death of which brother in 642?
Alhfrith: Alhfrith or Ealhfrith (c. 630 – c. 664) was King of Deira under his father Oswiu, King of Bernicia, from 655 until sometime after 664. Oswiu: Oswiu, also known as Oswy or Oswig (Old English: "Ōswīg" ) (c. 612 – 15 February 670), was King of Bernicia from 642 until his death.
i don't know