Is This Wrong?

I've been in love with my stepsister, let's call her "Lisa", for years. Honestly she was one of my first crushes, and she even said in passing conversation that she thought I'd make a good boyfriend.

I used to keep a computer journal with my fantasies about her. I even once got up the nerve to tell her about my feelings.

She wasn't really surprised, she said she thinks more stepsiblings are attracted to each other than will admit it.

We never pursued anything together, and our parents are not married to each other anymore.

Given the opportunity I'd love to be with her, and since there's no biological relationship, I don't know if that's wrong or not.