12 year old pitcher

Hey guys, im new to the site, so this is my first post…im a 12 year old pitcher . im about 5’2 120 pounds my fave positions are SS and pitching. My brother is a pitcher also and studies pitching so i look to him for advice when i pitch he says my shoulder opens up way to early… is there a way to prevent this from happening?

practice and a vid would help

There are a number of possible causes of your opening up early. So, like adamsmith44 said, some video to look at would be good.