I love my little sister to death and don't understand what's so wrong with it

I love my little sister more than the world, and every day I feel worse knowing that my love will never be reciprocated the way I want it to be. I'm 20 years old and she's 18, we're beyond close and I've had to endure the disgusting looks and whispers from people who are okay with this kind of love if it's between two adults of the same age, race, or sexuality, but for some reason, incest is considered sickening when it's consensual and doesn't involve abuse or harm to the younger sibling. It's hard to understand why, when I've read countless posts about people who have successfully married their siblings and have children with them.<br><br>I'm not sure what the future holds for us, but I want to be with her. She doesn't know how I feel yet.