I think initially it started because I was making an active effort to ensure that neither one felt I was choosing one side over the other (which SO often happens, and I despise). At least, that was the initial reason. Now it's just that I've gotten so comfortable with both of them (individually or with friends) and have grown so accustomed to us being available to each other, they're just the people I think of first when I want to do something.
Don't get me wrong... I'm not expressing discontent or uncomfortability or anything... it's not that I think I should spend less time with anyone, or that I feel like I don't have time for others. It's just that it's weird to me that the time I DO spend with friends is, more often than not lately, with two very good but mutually exclusive friends.
These two people are ex's with EACH OTHER. That's what makes it difficult... not ex's with me. (my fault... totally obscure... tx)