In lieu of a baby book update.... We won't know how big JJ has gotten until next appointment (a couple of weeks from now), but just past four months, he's filling out 6-9 mo. sized clothes. If you put him on his tummy he can pick his head up very well, and he'll sometimes roll over, because he doesn't like being on his tummy (one significant difference from his sister there). Sometimes, of course, he'll just kick his legs and screech in frustration because he can't get any forward motion.
His reach is getting steadier, and he can get his hands to his mouth pretty dependably, so anything in reach is liable to be thoroughly gummed. He smiles a lot, "talks" a lot (still mainly vowels though), laughs once in a while, and he's starting to find blowing bubbles to be fun. He can't quite stay sitting up on his own, but he likes to be held that way so he can see what's going on. He sleeps for a very long stretch most nights.
In sum, all milestones are go, and we think he's the best little boy ever.