JustTurned40

One data point wrt to your friends with children who seem depressed and isolated. They’re def sleep deprived. And complaining is a sport (I practice it a lot 🙂 ). Regarding the isolation…
If their friend group is broadly childless, it’s very hard to keep those connections. People don’t get that your life is different. The party you’re planning at 7pm requires they get a babysitter, the party you plan at 9 is after their bedtime. The lunch is clashing with nap,and saying “kids are welcome” won’t fix it. Keeping in touch with a new parent requires understanding their imposed constraints.
Consider – offer to babysit their kids for a bit, give them a few hours off. We’ve done that with our friends when we were the childless ones. Having a village (a group of parents who get it and will help each other however they can) makes a world of difference.
I meet a lot of parents who are reluctant to ask for help from the people around them. I don’t know why that is :/
(Disclosure: once you have toddlers that is much more sensible)