>>513615697
>#1 You will just not be sexually attracted to them no matter what.
This is correct. It's called the Westermarck Effect. And yes, I have sisters and I am quite disgusted by anything sexual related to them. I'm also the youngest child and my sisters are close to me in age. But I have heard that siblings with large age gaps don't necessarily exhibit characteristics of the Westermarck effect.

https://en.wikipedia.org/wiki/Westermarck_effect

On the other hand, people who didn't grow up with their relatives, and who meet them as adults, tend to be very attracted to them. This is because you are most attracted to people who look like you.

https://nypost.com/2023/07/04/people-are-more-attracted-to-those-who-look-like-them-new-study-finds