Castle's Unknown Son

Castle and Beckett meet at a party. Castle is 24 and Beckett is 19. Beckett gets pregnant with Castle's child and she is in college. Castle already has a daughter but later down the road he runs into the detective he slept with more then once but doesn't remember much of it. What will he do when he finds out he has a son? Read to find out and I don't any of the characters just having fun with them is all. WARNING: SEXUAL CONTENT....