J was born with curly hair, but much less curly than it is now - probably 3a/b (I'm 3b/c and his daddy is 4b, for what the numbers are worth.) Now J's hair is 3c at least. It got gradually curlier and was probably not this curly until somewhere between 6-9 months.

I was born with much straighter hair as well - I was probably a 3a until I started school.
Get used to me. Black, confident, cocky; my name, not yours; my religion, not yours; my goals, my own; get used to me. -Muhammad Ali