DS1's obsession with his best friend....what's the best thing to do?

[robin3]

DS1 is 4.2yrs. He goes to pre-school and since joining he really loves it. Term 3ish we became aware that he had a firm best friend and of course we were really chuffed. We often do playdays. He also gets invited to playdays with other class members which he also enjoys and he seems to have quite a few friends. His BEST friend however, seems to be a bit of an obsession so

1. every night we have to weave him in to bedtime stories
2. DS1 always corrects any talk about his friends with the fact that his BEST friend is his BEST friend
3. He gets unreasonably jealous at Birthday parties if anyone else over dominates his best friend and seems to immediately banish them

At the last parents nights the teachers raised it along with lots of nice stuff. Their thoughts on it were that it's a mutually kind friendship but that DS1 tends to hold back and let his best friend do most of the talking. They said that DS1 is very kind to the other children so that was reassuring. Also we discussed what's best for next year when the boys will be split in to smaller classes and they said that it might not be great to split them but we can talk about it again before September.

At the start of this term the teachers were obviously trying to break down some of the friendships in the class gently by simply forming groups for activities. DS1 and bestfriend were split and since that time, even though he's still in the same class, DS1 has gone on and on about wanting to be in the same group. I think he's also been crying a bit about it when the teachers have separated the groups for an activity. I'm struggling to guide him through this and I'd love to be able to help him chill out a bit about it so they can stay in the same class next year. I specifically chose the school because the kids go from 3 to 12 and having moved around myself a lot as a child I wanted him to make lifelong friends, yet I find myself thinking it might be better for him to be in a different class next year.

So...any experience of this, suggestions about how I can help him, thoughts about the split? It's been over a year now so I don't think it'll just fizzle out in the short-term.

You have to do something about this now, which might sound an extreme statement.
I suppose I am biased as, DD had a friend and all the way through to yr 4, she got extremely jealous of any one who 'monopolised' the girl. Then the other young girl, had a party and invited the whole class except dd (an over sight ... I think) it was the best thing that ever happened to dd, although it didn't seem like that at the time. It meant that she had to have a think about who to be friendly with. I appreciate that girls bond much more extremely than girls. But, if it was me I would start inviting as many different kids over as I could so that he could make other friends, not not inviting BEST friend iyswim but best friend one week, a the next, best friend the next, then b etc.

Thanks violetskies...been away hence delay in response. Thing is we do loads of playdays with other children which he enjoys but still we default to the same best friend.