Board Thread:Warhammer 40k General Discussion/@comment-14745711-20140911102114/@comment-25177957-20140913225820

Well the Emperor was birthed by a woman within a primitive, hunter-gatherer villager in Anatolia. None other details are given about the families the Emperor once belong to if he even bothered with such mundane and human things.

The warp can't reverse time (only fowards time), and nether can the Chaos Gods exactly. The Old Ones were known to have a portion of the power to reverse time, and the Emperor also does not have the power to reverse time, else he would have rethought creating the Primarchs lol.