I think it's totally normal for you to feel this way and I don't think it's too much for you to expect them to make a bit of an effort to keep in touch.
If they're friends with the ex though then perhaps that's got something to do with it?
If you really really value these people as friends then I might suggest sending them an email telling them about your concerns and your feelings and see if they how/if they respond?
Posts
Re: What do you guys think? (friendship-related post) - long
