It's morally unacceptable to have relations with a child.
Steve has raised his step daughter for 5 years now and is starting to fall in love with her.
Steve wants to show his step daughter how much he loves him.
Steve makes sure to buy his step daughter whatever she wants.
Steve asks his step daughter if she wants to be his girlfriend.
Steve's step daughter feels loved by Steve and is happier.
Steve's step daughter feels pressured to say yes and doesn't feel comfortable.