I would never consider having sex with any of my (known) biological relatives, not because they are biologically related, but because they unfortunately are just not attractive to me. I do remember when I was really little chasing my older sister around the house demanding that she kiss me, but that was simply because I was too young and naive, and had not realized that her and I would never work out.
1. She's blonde
2. She's lesbian
3. She's married
4. Our taste in anime are completely different. She likes shounen trash anime that goes on for 30 seasons, where as I like short psychological thrillers. I wish I had an older sister who was also the perfect match for me romantically and sexually.