Some are proper uncles and aunties in their 30's even. Some your age are acting like kids still and you are married. Doesn't this mean these stages aren't rigid and are different for everyone?
For me it's more about the passing time, it's a bit unsettling. I think about how fast time is passing by and our time on Earth is so limited. I haven't made the best use of my time, maybe if I start doing that I would feel less anxiety about age.