Hey height comes when it comes, and even if he was short forever, than if he adapts it will become his strength. With regards to acting like a younger kid, don't even worry. People grow at different rates, and furthermore, those that are different are those that see things differently, do things differently, and end up changing the world. I still hold many child like characteristics and I am 23, and they have repeatedly shown to have helped me in multiple ways. Someday in the future your brother may grow into enjoying other more older interests but until then and forever after I will give the same insights I came to realize in the middle of high school, "screw everyone else, you only get one life and this is it, so do what you want and what makes you happy, and do not worry about if you will look cool, just be who you are because that's the coolest you can be. Oh and what I found after I realized this was that when I acted the way I wanted, when I was free and natural, that was when I actually became cool, now that may not work for everyone, since some people's natural state may not be seen as cool by society, but what is universally seen as cool, is being confident in who you are, and not worrying about what others think.

I know this post is old, but I had already started and figured I would finish, hope your day is awesome.

What kid things is he interested in? Are your parents small people? He will grow more in the next few years, but might be only 5'8 as a grown man. Just allow him to grow and mature the way he feels comfortable.

@XNexoX
I feel short, there are people that are taller than me at my school.
There are many tall people in my family pretty much most of them.
They are taller than me. I wish I could be 6'4"

@RubyHeart
Alright, I'm 27 and 5'3, and I don't complain about my height.

Different people mature at different rates. Give him space for a few years.

@RubyHeart
Only? That's not short. I don't know why you were expecting to be really tall anyway.

I'm only 6 feet tall now :( That time will come. some people just takes alittle longer.

Like I was . Something's stay small. I'm 5' 11' tall now

@Gallantio
Have to make sure he ENJOYS the sport, though. Most of them are just plain boring. Kung fu had it's fun points [except the memorization], could try boxing. I never liked running around caring about balls, he might not either.

What is the "little kid stuff" he likes? Examples?

@XNexoX it's just that you said "Being tall isn't such a big deal."

@RubyHeart What does it matter?

I was 5'3" when i was 12 years old :)

Anyway, I can't have an opinion on this if I don't know what he does that you consider childish.

@XNexoX I'm going to the gym already, but how tall are you?

XNexoX okay i'm only 17.

@RubyHeart
Just get some muscle on. Being tall isn't such a big deal.

I'm not saying there's anything wrong with being short. Heck, I'm only 5' 1" I'm saying he needs to grow up and get interested in the stuff kids his age are interested in.

Oh my god. Are you that height troll too?