First of all... Anytime you mix with family, be it though marriage or incest... your asking for trouble
Second of all, if your engaged to someone and wanting to be with or stay in contact with someone you were with, that isn't being fair to your fiance. It also shows that you're not ready to be totally commited to one person.
Thirdly, I personally can't stand to be with men I don't have anything in common with. You're going to get bored with each other if you don't share common interest or goals.
And #4, I
SERIOUSLY doubt the reason you're ex step brother isn't keeping in contact with you is because you hurt him. He obviously got tired of waiting for round #2 and moved on. Trust me, if a man really wants to be with you, sexually or for any other reason, he
WILL get in contact with you.
Anyways, theres my 2 cents. Good luck!