I would give everything up to be my sister's husband. When she was sixteen and I was twenty-two, I asked her to be my girlfriend. She said no, but held my hand and kissed my cheek. Totally worth it.
I actually tried making a move on my sister. She was disgusted and we haven't talked since. Now everyone knows me as the guy who wants his sister. But I still want her and would not hesitate if I had the chance