At what age do you find that your young boys tend to finally fill out and 'bloom'? Thanks!

I'm also waiting on a boy I'm running on. He's 11 months.
I think it all depends on lines on how fast they mature.
Most I've talked to say boys start coming back together at 18 mos and in prime at 3 or 4 years. Some probably sooner while others are late bloomers.

My boy is 18 months and has just blown his puppy coat. I'm hoping that he is on the "early bloomer" side!