I grew up with two identical twins from elementary school onwards, and it was always super easy to tell the difference. They were completely different people to

I grew up with two identical twins from elementary school onwards, and it was always super easy to tell the difference. They were completely different people to me (and had really different personalities, which might have helped). In high school, another pair of twins arrived from one of the other middle schools, and I was never able to tell the difference between them, even after 4 years. Why is that? I would guess is has to do with exposure and knowing them from an early age. It's weird how that works, but I imagine parents of identical twins can very easily tell the difference, so there must be some major difference. Recently, I met another pair of twins and I couldn't tell the difference between them either. It must be extremely nuanced and only obvious to people who have been around both twins for a while. I would guess that it would be easier as twins get older and diverge in physical ways (body fat, muscles, and other physical traits).