One is my best friend, though I have no idea if I am their best friend.

That’s an awful feeling, and one that I’m quite familiar with. I’m pretty sure I’m not my best friend’s best friend, and that sucks to think about. It can definitely make the relationship feel one-sided, and that’s painful to consider. Try not to put too much stock into quantifying your friendships, as it’s very easy for that thought to spiral out of control.