No, sorry Thomson - From history.com (there are plenty of others as well if you care to look)

It is known that St. Patrick was born in Britain to wealthy parents near the end of the fourth century. He is believed to have died on March 17, around 460 A.D. Although his father was a Christian deacon, it has been suggested that he probably took on the role because of tax incentives and there is no evidence that Patrick came from a particularly religious family

Never heard of his brother being a bishop in Brittany - although I am happy to accept any eveidence to the contrary.

BTW - What did Pat say when he was driving the snakes out of Irleand?

Looking back over his shoulder from the driving seat -

"Are you alright back there, lads?"

:D