Ha. I like this idea, especially as you've laid it out in your comment below. Could be a very sweet story -- maybe a little humorous along the way too. Lots of possibilities. Good luck! I'll keep following.
Thanks for looking at my idea, I was approaching it in a very romantic manner, his dad being a sort of Casanova, spreading the seeds of his one night stands around the world and John going out to unite all his step-siblings...but you know, you have given a very interesting twist to my story so let me see if I can develop it along the lines that you are imagining :) Will keep you posted.
It may be obvious to some, but not to me... is this a story about a demon that has fathered numerous offsprings? and the protagonist is wanting to prevent one of them from heralding the end of time?