You probably aren't able to start a group & steal/coax/invite those from the "outside" group but it would sure be a nice idea. They had to have experienced that left out feeling.

We're those people invited to be part of the "in group" but chose not to participate with them. There are times when I have so many other activities that I have actually made a conscious choice not to be involved. Especially when I feel less of a connection & it doesn't bother me that they talk about their activity because I was the one who chose not to get involved (though group should focus only on that groups functions)

I think you are perfectly correct in the way you handled this. Sad it came to this point.