Do your children outgrow friendships fairly quickly? DS is a friendly child and plays well with others, but does not really have a lot of friends. Shortly after a friendship develops, the other child starts to get competitive (typically unbeknownst to DS who is just happy to play). When this happens, the other child starts really displaying self esteem issues which are a turn-off for DS. Then he is no longer interested in a relationship with that child. He would rather play on his own than be subjected to someone else's emotional issues. Can't say I blame him. We have seen this with both male and female friends.
In a bit of a hurry, so I can't really go into detail at the moment, but one thing that strikes me about the description here is that there must be something more to this than the "other" child's emotional self esteem - even though one child is EG or PG and the others might not match cognitive insight, if you took a broad sweep look at children in any one age group, you should find kids who are all over the place on self-esteem and the likelihood of one child's behavior impacting their own self-esteem.
Out of my 3 kids, I have 3 very different personalities re how friendships are formed and how they last. In each instance, the lasting component has little to do with the "other" children but is more related to how my specific child develops/uses/approaches/values the relationship with the other child. I don't mean this in a negative way at all and I'm not suggesting that your child has an issue with how they are approaching friendships, just suggesting a look at it from a different direction rather than assuming the friendships aren't lasting due to blows to the other children's self-esteem.
Hope that makes sense -
Best wishes,
polarbear
