I don't know the exact names of the brothers, except Judah who sing benjamin calypso, and Reuben I think, sings those canaan days. also, one more angel in heaven is sung by a brother.
as for your other question, yes the prisoners can be doubled, because that scene goes directly into go, go Joseph which ends the first act, and the brothers are not in the show from close every door till the end of the act.
"I'm an American, Damnit!!! And if it's three things I don't believe in, it's quitting and math."