I'm the older brother of identical twins. I can tell you that they can be both startlingly similar and startlingly divergent.

For several years during their childhood, I was the only one in the family (2 adults 5 kids) who could reliably tell the twins apart. They would regularly blame stuff on the other twin. And get away with it.

One ended up as a very-liberal TV producer and the other ended up as an evangelical preacher.