Do you feel bad having a favorite sibling?
I'm the middle of three and I'm way closer with my brother than I am my sister. We're all about two years apart, so I went to high school with both my sister and my brother (my sister was a junior when I was a freshman; I was a junior when my brother was a freshman).
Point is, we had equal amount of time together growing up and had similar interests (read: sports) but I just clicked with my brother more. We talk all the time now as adults; I rarely talk to my sister.
Not because of a falling out, just because we never really clicked. And it's something that really weighs on me. I want a closer relationship but at the end of the day, I just don't think we'll have one. We love each other and all that, it's just, we don't mesh, I don't know how else to describe it. She's a lone wolf and I love a pack.
My guilt about this keeps me up at night, even though I don't think either of us have done anything wrong.