Yeah...... I think there might be a correlation to why he has no idea what's going on in their lives.
In my experience really large friend groups like this are typically the result of something like a frat house or some kind of club. It's more activity based than it is cemented by any sort of deep emotional relationship.
I'm not really a fan, I prefer more meaningful relationships. I only get to see my best friends like 1 a year, but I am also friends with their partner, I know what they are teaching this semester, I talk to them about their research and let them bounce ideas off me, and we try and make time for each other. To me having a friend I don't have a deep emotional relationship with is like making small talk about weather to strangers.