"At age 71, I don't have time to do things I don't thoroughly enjoy, given the choice and opportunity."

And that's the reason they're dropping stepfam.

Seriously, I find a lot of give-and-take in cycling, especially in group riding. We had an incident a while back where one rider took off, group followed, at the next stop, the person that took off was soundly cursed, etc. That doesn't need to happen. There have been times when the group dropped me, and I was sort of peeved about it, but then there's been times when I dropped others, and times when the group waited up for me, and times when I waited up for even slower riders. Just remember that no good deed goes unpunished, and just because you wait 30 minutes for someone to fix their tire doesn't mean they'll wait 30 seconds while you change out water bottles. The secret is to just let any little slights just slide off like water off a duck, and then you can enjoy the ride the next day, too.

And Stepfam, a specific suggestion for you: Try something like "How about riding my pace for the first ten miles so I can ride with you a bit, then y'all can take off after that?" And maybe get some good feelings on both sides about it, rather than them feeling stuck or you feeling dropped.