Children of the Darkness: Dark Beginnings!

What if Voldemort captures the Potters as they were celebrating with their friends about the news of them being with child. The plan is to cast a spell on Lily so that apart for carrying her child, but with his too. But things don't go to plan... how will this and other things change the story line. Full Summary within. No pairings for now! Mainly OC centered. Rated M for a reason!