I have namechanged for this and I am going to have to be deliberately vague to avoid outing myself. But I can't really seek opinions in real life because those I'd usually talk to are those involved in the situation.
A few years ago I went out with my first proper boyfriend. I thought he was 'the one' at the time, as you do. A couple of years later, when I went away to uni, he ended things because he wanted me to be able to live the full uni life and didn't want a distance thing. I was all for giving up my uni course for him, but was persuaded not to. We stayed in touch, remained the very best of friends, because there was no reason not to be. I was devastated when he started seeing somebody else, and it was hard to stay friends but somehow got through it. Fast forward a bit and I still consider him my best male friend. We can talk about anything and have supported each other through rather a lot of difficult times, on both sides.
Recently he asked if I'd mind if he asked out my best female friend. Initially I was really excited by it and thrilled for them both, I think they are well suited and get on well and think it could be rather special for them both. They are now dating, and have quickly discussed marriage and babies and it is getting very very serious very very quickly.
I desperately don't want there to be a 'but' here, but there is.
I am finding it really weird. Because I am so close to my df she tells me literally everything, all that he says (ie. she's the first person to make him this happy, the best in bed, etc.) and all that they get up to in rather too much detail. And I am finding it really hard to listen to, it doesn't seem to register to her that this could possibly be weird, despite knowing our history. I didn't think it would feel like this until it happened. The thing is, I know I can't possibly remain as close to him as I am now if I am to stay close to my df, she has already made a few comments which indicate that. So I know I have to step away from one or the other, to a certain degree. I could never let either know that I feel like this because fundamentally I want them to be happy, as they appear to be with each other. So I'm all smiles and saying the right things but internally a bit, well, scared of the changes that are happening as a result in my own friend-relationships with the two of them.
I think I just want to know that its ok to feel a bit sad strange. Or, if I'm being (internally) unreasonable, could you gently let me know? If others have dealt with similar better than I seem to be, a kick up the arse bit of friendly advice would be most welcomed.