Arthur
Arthur was born Eric Powell. His parents were Welsh and he was born in London, an only child. He grew up in Oxfordshire and had a childhood that, in retrospect, was idyllic. He had lots of relatives living nearby, holidays in Wales and, with all childhood memories, those holidays have morphed into a paradise where the sun always shines and it never rains.
Arthur was very middle class and very well off. Both of his parents are doctors and his mother also had independent wealth. Arthur wanted for nothing growing up but, somehow, he wasn't spoiled. He attended public schools in England and went to Oxford University. He was raised in the Church of England and, when he was twenty, he legally changed his name to Arthur.
He's extremely well-adjusted and has insight enough to know that he owes a lot of that to his parents this time around. All he lacked as a child were siblings but now that he knows Morgan and Morgause again (awkwardness aside), he certain feels his lacks nothing.