Ok, so I have a strange question: am I over developed? I have taken the Tanner level calculator and I'm at stage 2.5. The thing is I've compared my penis and genital size to my older brother, who is 16 and I'm 13, but I'm bigger than him, While I'm 3 inches erect, he's 2 inches erect. My testicle size is 6, he's 4. He's at about tanner stage 3 and started puberty a long time ago, I think at 10. But he's way smaller than me in size and shape. Am I over developed?
Comparing between two individuals never works because we are all different, even when you are from the same family. Two people can have greatly different shoe sizes, they can also have different genital sizes, it all depends on the genes they inherited. Not only does size vary, but starting times and speed of development also varies between individuals.
If your brother first noticed changes at the age of ten, then he is developing at a slower than usual rate. The typical rate of development is about two years per stage for males. The length of an erect penis doesn't say much, in part because a part of length is how skinny or fat you are. The more weight you carry the less of your penis you'll see because it is anchored internally. A layer of fat will make the penis appear to be shorter than it actually is.
What it sounds like is that you are developing sooner or faster than your brother. So for a period of time you might match or exceed his stage of development. It won't make much difference because in a few years you'll both reach stage five and be at the same point in development. You're sizes will still defer between the two of you. You won't necessarily be the same height, have the same shoe sizes, wear the same pants size, etc. But that is because you are both unique individuals.