Umm how odd. I met Mr Monkey when I was 27 and he was 36.
I'm 45 and one of my favourite people at work (we often lunch together and go for drinks) is 29.
As long as there is no exploitation friendships across generations are a good thing.
I think because a lot of close friendsbips are formed in education we see friendship groups of the same age as the norm/most desirable but a range of friends is good.