Im assuming it was approproiate sexually, I think you and his father need to have a long and serious abouy how wrong he was to touch his sister and he's too young to do that kind of thing at his age. And explain to him about the birds and bees if you havent done so aready. also. Take him to church if you havent because it will help him learn good values. not that yore not doing that. get involve as a family going to church. BUT I WOULD TAKE HIM TO A PSCHOLOGIST TO MAKE SURE THAT HE HASENT BEEN TOUCHED INNOPROPRORIATLY ALSO OR ASK HIM YOURSELF. i THINK HES JUST CURIOUS AT HIS AGE. BUT JUST IN CASE THESE DAYS WITH ALL THE HORROR STORIES YOU HEAR ABOUT KIDS BEING SEXUALLY ABUSED YOU NEVER KNOW. I do think you and his father should be honest with your stepdaughter mother about the sitution since if she found out about otherwise then she may trust you and his father again. and talk to your stepdaughter too about the situation. good luck
