Is this normal? I think my 19 yr old stepdaughter is really hot?

[Yera]

How old are you? If you're around her age - mid 20s (O_O Mum's a cougar??), then it's hormones. But you need to learn how to control them. She'd most likely be disgusted at the idea, so DO NOT tell her. Tell your wife first, if she seems like a nice lady (you don't want her to start abusive her daughter because of this). Why don't you like your wife more, try to remember what it was that attracted you to her? But really, you should split with the mum if you can't act like a father.