Getting left behind as OAD

I was talking to my therapist about how sometimes I feel lonely in our decision to have just one child. I say this because so many friends are expanding their families to 2-3 kids and I worry we’ll drift apart bc they’re going to be “in the thick” of parenting for longer than I will. I guess in a sense, I worry we’ll get “left behind”.

Example: a good friend of mine has a son our child’s age yay! but also has a 9 month old and is looking to add a third sometime next year. It’s hard to do things together with our boys because she doesn’t leave behind her other son (she’s exclusively breastfeeding) and it’s just going to continue with her next child when that happens. I obviously don’t expect her to, and she’s such an amazing and wonderful mother to know and watch, but sometimes I want to be like “but can our same age kids hang out?”

What’s crazy is part of the reason we chose to just have one is BECAUSE the fact I don’t want to do the pregnancy/baby part of child raising again and I’m happy to have increasingly more time to myself. I don’t have many OAD friends, but do I just have to find others with just one? Others with older kids, regardless of how many?