Two alien brothers on a intergalactic graduation road trip land on primitive Earth and manipulate the simple life forms to evolve into humans. They stick around for a few millennia and eventually establish the afterlife with each one overseeing particular domains. They host a discorporated philosopher named 'Yeshua' who says he only wanted people to get along - but got crucified for that. They must ultimately protect Earth from one of the descendants of a Holy Roller who sincerely believes she is descended directly from Adam and Eve. I recall their names are something like Brin and Colu (reminiscent of colubridae - a class of serpents, who is the younger brother and is not in revolt against his brother - just a little jealous).