Ours was a parents group set up by the council. When we started, we had 3-5month-olds, and they were only children for all of us.
TBH, I really didn't like it at first! I didn't feel as though I fit in.
But I kept going because it was an activity that was cheap, LOL. Now, our kids are 2, we have new members and we have set it up like a playgroup with activities/craft/singing etc. I love it. And I have made a couple of fantastic mates. It just took us some time to get to know one another better.
Interestingly, I didn't think I fit in at first because many of them are 10 years older than me. But the older ones are actually better friends now than the ones closer to my own age.