For me it's difficult to accurately guess (actual age or within 1 yr) from just a single pic, even during the rut.
There are aspects of this one lending towards 5 1/2, others that lend towards 3 1/2.
If I had to give my best guess as to his age now, it would be 4 1/2.
I made my first "guess" before that 2nd prior year pic was posted.
Having seen what he looked liked 2 years prior, my revised estimate become 5 1/2 or older.