Gosh, that’s really tough.
Any ideas as to why he’s been dumped by the group? If they’ve been friends since the age of 4, presumably you know the parents. Any chance you can sound them out on it? I mean, I know that probably won’t be a lot of use, since you can’t force kids this age to be friends if they don’t want to. But maybe it might shed some insights.
I have an about-to-turn 15YO who has had a group of friends since the age of 4. They are generally starting to break away and form other friendships - that part does seem normal. However, for the most part, they do still see each other, as well. Having said that, the only time they really get together as a group is when we Mums have a catch-up over a Friday night glass of wine, so it’s not really of their instigation….
What I’m trying to say is that I think it can be very normal for old friendships to start to recede as they figure out who they are as teenagers, and as people. They start to realise they have more in common with new people, and the focus becomes on those friends.
This means it’s not a reflection on your DS, per se. The kids are probably just gravitating towards more like-minded souls. And it’s your DS’s opportunity to do the same.
It’s hard getting this message through to 16YO kids, though. They will look inward and blame themselves, instead of realising, in the nicest possible way, it’s not all about them.
Hopefully you can have some convos and explain this is a normal passage of life, it’s not about him, and to use the opportunity to branch out and get to know new people.