The only difference is the small earring.
The boy on the right is wearing a black stud earring, while the boy on the left has no earring.
Everything else—including the striped shirt, shorts, watch, bag, shoes, hairstyle, and pose—appears the same.
The tiny detail is easy to miss because it blends into the dark hair and facial outline. The answer is the earring on the boy in the right-hand picture.


