I really don't know...
Are the ages supposed to be very similar in these photos?
The larger teeth on the R could be permanent teeth coming in; but the shape of the smile is completely different, hairline appears to be very different, upper lip on R is much thinner than upper lip on L. Ear on R appears to have more of a sticking out lobe. Eyebrows on L appear to slant outward/downward more than on R.
Here's a pic of when the front teeth fell out. The middle two should be switched as the one on the right is younger by two years from the one on the right (sorry, just pasted it in from your post). The last one is the oldest.
Seems to me the same kid as he has grown into his buck teeth in the next to the oldest picture.
He was thinner in the youngest picture and gained weight as he grew older.