Those who look so much alike are often very different people. It can be seen even on photos.
Since childhood parents who can't see any evident difference between twins start "endow" them with different temperaments: one smiles more often, another one is often angry; one eats much, another one easily falls asleep. Parents do not often apprehend that this starts to influence further maturing of their children.
Rustam and Nadir, 11 years old
The boys study at school and have not exploited their resemblece yet. Nadir is naughtier, Rustam is assiduous and calm, he often has to help his brother out of troubles.
However twins almost never have similar characters.