Hard to accurately guess from a single pic, but I believe that one is 3 1/2 or older.
Hopefully, he is 3 1/2, and you can look forward to him gaining a lot of mass in the coming year.
I certainly agree that 2 1/2 cannot be ruled out, just based on this one single pic.
That would fantastic if he's only 2 1/2!
But 3 1/2 remains my best guess.