<human>: Can you give me the gist of the text in a nutshell?

Sorry, this post might be an angry rant as well as the situation and probably sounds stupid. 

My brother is, what you could say, the golden child of the family. My grandma was in town and all he did was ignore her and give her an attitude (Hey can you take the garbage out for me please? *huffs and rolls eyes* "whatever."

She lets him get away with being rude to anyone, right in front of her, even herself. It's all excused, all the time. It's getting to the point where I get so angry at how much of a dick to me and my grandma that I'm punching the chair in my room so I don't punch him in the face. 

He never cleans anything, never does any chores, if he doesn't get his way then he throws a fit and slams door and cusses under his breath, and he also leaves the house whenever he wants to even when my mom says no, and just yells at her. But it's okay, because "he's young" whatever the fuck that means. 

When I was his age though, I was verbally and emotionally abused by my mom, constantly put down and never allowed to go outside, couldn't do after school sports, was always grounded and forced to do all the chores in her house like cleaning the kitchen and bathroom and folding her laundry, all the while being called names like "fat" and "asshole."

What can I do to make my brother less rude? If I say anything to him, he runs off to my mom and says I called him something else or makes something up and my mom then calls me "disciplinarian" that's "so mean to him".

Sorry if this is a dumb post and sounds like sibling rivalry, but she's also a narcissist so I can't talk to her about it. She's perfect in every way in her mind.
<bot>: Mom lets brother act incredibly rude and selfish to grandmother and I, and blatantly disrespects our mother and she doesn't care.