did you ever see two puppies?
if they are the same breed, it's often hard to tell them apart.
People are like that but we don't call it a 'breed'.
two people can look very very similar. Dads will look like their sons.
you know this. Why does this confuse you?
even unrelated people can look very similar.
you have to get to know them and then it's easy to tell who they are. Like two puppies, if you know both of them you know which is which. Simple.