Well said @5YearsLeft
I'm in my late 40's and have had, I'd say, 3 'chapters' in life so far. My friends are the same andi I can see how those paths have played out differently in various people.
So, to me you're in one of those, but because it's the child rearing chapter and you're young, you are struggling to see beyond.
My chapters were the wild years travelling and parties, the earning years with reasonable money (for me, it was never over 40k) and enjoying being and building life with DH, currently where you are in the child rearing years (11&13).
But I have friends who did similar chapters but in different order.
We're all old enough now, to be at the point where we can see that those who looked like they were winning at life at 30 and had everyone else feeling like they were doing something wrong, have since ridden more of the roller coaster of life and have had their share of ups and downs.
We have reached the point where we just celebrate the good and commiserate the bad cos we've all had a share of both.
My sister lives in Oz, on social media she looks like she's totally living the dream. But she envies me my proximity to family! And the sunshine is sometimes a bit much, her house was at risk of fires, she and her husband have almost split more than once and she was far from family support... and one of her children has a mullet 🤣🤣 (haha that one's just a joke, don't come for me).
The age of your children are often the claustrophobia years (from a personal pov... and the delightful years yadda yadda, of course), regardless of whether you have previously spread your wings or not. I'm in the trenches with you, but at 48 I have less time ahead to mix things up again - but you are the other way round - you're doing your chapters just in a different order... Lots to envy about that. My work colleague is the same but ahead in years and the adventures she's having are fabulous! But she has so much fun with her adult kids in the mix, enviable, my adventures were wild but sometimes also lonely as I was solo.
That said, I'm plotting my next chapter now which will be self care and supporting interesting projects in my area. I'm planning on conquering mountains and lakes and getting stuck into meeting really interesting people by involvement in new job/volunteering.
Your feelings are natural, but also unfair on yourself and skewed by the fact that your sorry hasn't fully played out yet. All the people you are seeing have greener grass are, I guarantee, looking at your field and seeing your grass is very green too... Because you always see what others have that you feel is missing, that's just the nature of it. You don't see their 3am thoughts.