I have a hypothetical question?

Ummmmm, not so hypothetical.

I guess it would depend on how long you've considered her as like a sister and not just a friend. It would probably be a little weird, but over time as that sister-ness fades, it might be okay. You can really only judge for yourselves.

Edit: well, considering what you added, I don't think it would be overly weird. Both girls are into it and there's no real sense of being family members. It might be a tiny bit weird for the step dad, depending on how long he thought she was actually his daughter.

I think it would be EXTREMLY disrespectful of your step father and your mother because though they just found out he probably still considers her his daughter

I personally think it's a little strange, but I suppose because they're not related it would be okay.

As long as they're both happy, eh?

ur very confused!!! are u worried about morality n shtt like that but then ur ready to sleep with another girl??? its the same crap! might as well and do it regardless of who the hell she is

Do you have genuine feelings for her? If so, um..... I guess so. There wouldn't be reproduction, so, nothing will go wrong, I suppose.

maybe you should check to see if she is into it.