Is OTHER wrong in the post ? POST : For starters I dont use reddit very much so I'm sorry if I'm a bit out of the loop on things. I also apologize because this story is LONG.

Before we begin this story, I'll tell you about the main people: 

Me- a 20 y/o guy who is basically the mediator between my grandmother and my mother since I'm the "good kid"

Older brother(OB for this story)- A 22 y/o redneck who is very bad with money and has just had a baby with his girlfriend

Mother(Mom)- A 38 y/o mom who had her kids taken away when we were young due to her drug abuse. She cleaned herself up and now lives with my great grandmother (Granny) taking care of her.

Grandmother(Gma)-Gave up her future life to raise us kids when our mother was battling drug abuse. Some of the kids still live with her


So to start off with, I have many siblings (all half) but I'm only close with the 4 that are on my moms side. OB was living in a camper (which is like a mobile home but twice as small) behind Gma's house when he found out that his gf was pregnant with his kid. OB is shitty with money, he usually spends his paycheck the day he gets it and asks to borrow money afterwards. He would spend it on stuff like guns and things off FB and Craigslist that he would just sell in a week for less than he bought it. Before the baby was born, Mom and Granny (this is Gma's mom) decided to buy the baby about $1000 worth of baby stuff. They then offered for OB and his to stay at their house when the baby was born because the camper wasnt a suitable place to live period. The door was coming off, animals have died in there, it was just disgusting beyond repair. When the baby was born, mom started to obsess over the baby. She would hold it more than OB and his gf would and she would always call it "HER grandbaby".

 I already knew that OB and Mom living together would be a problem. See, OB is a big guy, about 6'2 and was husky, but it was completely muscle. He always threw a fit over everything, partially because he had ADD and ADHD but also because he was used to a lot of privellages from working for my grandfather. When he would throw a fit, he would yell and scream and get in your face and try to make you back down. We've dealt with this so much that we knew he'd calm down as long as you stood your ground and let him vent. He never hit any of us in those kinds of fits but he always looked like he was going to break you in half if you dared to smart off.
Mom, on the other hand, was different. She was like a manager 24/7. She is always super cool about a lot of stuff and is generally fun to be around as long as you respected the place and everyone in it. If you didnt, it was like a switch was flipped in her brain. The way she dealt with conflict was like "Its my way or the highway, and if you didnt like it, you better square up. Because nobody is going disrespect me or Granny on Granny's own property". She would look at you with a piercing look and refused to back down to anyone. She'd tell you in a very commanding voice, only raising it to express emphasis on words (ex. Don't you DARE talk to her like that in HER own home). And yeah, she doesnt back down from anyone. She'd tell someone off twice her size if she thought they were in the wrong without a second thought.
Needless to say, they were a bad match to live together.

Anyway, this next part is the incident that tore our family apart. Keep in mind that I heard variations of this story from OB, Mom, and OB's gf, and pieced together what actually happened.

OB had found a few chickens for sale on craigslist for about $40 and asked Granny and Mom if he could make a coop for them to lay eggs. Mom and Granny talked about it and decided against it, since they were buying dog food for his 3 dogs and didnt like that he beat the dogs. They made up some excuse to tell him "no" gently so he wouldn't throw a fit and cause problems. The excuse was "I don't like chickens" which was a poor excuse, but most people could tell that it meant no. He didnt. The next day he was getting supplies outside to start building a pen for the chickens when Granny saw what he was doing and asked him what was going on. She said something like "I thought your mom said we didnt want chickens". At this, he started throwing a fit.
Granny has about 230 acres of land that is mostly woods, and OB was promised a part of the land. He was already starting to build his own house there and that's where he was going to put the chicken pen. The problem is that the deed to that land wont be his until he's 27. Granny and Mom said that he can build on it, but it was still their land until then.
OB was throwing a fit, collecting things in the house because he "was moving out. He was tired of all the bs and not being able to do what he wanted on HIS PROPERTY". Ganny was trying to calm him down and reason with him ("Where will you go? That house isnt even built yet, you should work on that first", etc.) 
He wasnt having it. Still collecting his and the babies stuff, he was saying things like "that's my property and I cant do anything" and "Its just a couple of fucking chickens, what's the big deal".
At this point Mom just got home from work. Her husband, who was there while all this happened, started trying to explain what was going on while OB was cramming stuff into his truck. When she got enough of an explanation, she went over to OB and tried to reason with him, not for his sake, but for the babies. Saying stuff like "you've got nowhere to go, we have everything you need for that baby right here. I dont care if you go, but that baby needs to stay here."
OB was already furious, there was no reasoning with him. He started to get in Moms face yelling about how "ITS MY PROPERY, I CAN DO WHATEVER I WANT". Getting as close to mom as possible without touching her and staring down at her. Mom started to yell back at him saying "This is GRANNYS property, not yours! Granny said she doesnt want chickens, and what SHE says Goes!"
They keep arguing like this, as OB  takes a step forward and Mom takes one back. More arguing. OB: Another step forward trying to intimidate
Mom: Another step back still arguing
At this point Mom has her back against the front of her SUV, bending slightly backwards. OB is still as close as he can be, without touching her, in her face and yelling. Mom goes into "Fight or flight" mode, and she'll be damned if she runs from ANYBODY at her own house.
She punches him in the jaw and keeps hitting him over and over. I'm sure she got some good licks in, but OB is built like a bull. He grabs her by the neck and slams her against the car, not aggressively like he wants to hurt her (though I'm sure he probably wanted to) but to get her to stop hitting him. She screamed for him to let her go and he yelled that he would when she stopping hitting him. His girlfriend, who was outside with them the whole time, had to get inbetween them and break them apart. He started to walk towards the house, probably to get the rest of his stuff and leave, but Mom wasnt having it. She thought that he was going inside to beat up on granny or something. As he got to the front door, she ran infront of him and told him to leave the property and never come back.
He, with his gf and baby, left with whatever they had and went to Gma's house.

Now Gma was the one who raised us kids when our mom left. That was our home. When OB moved out to the camper behind the house, we had enough room for each kid to have their own room. Right now, OB, his gf and the baby are sleeping in the living room.

The problem that this post is referring to, lies here.

Gma and Mom have been rivaling ever since Mom came to live and take care of Granny. Rumors, whispers, and gossip have been talked about each other for a few years now. When they're out in public together, they seem just fine. But when I go visit either one of them, it's nothing but gossip and spite. I'm the one who always meditates whatever's happening and have brought them together and talked things out multiple times.

Think about that for a sec. A 20 y/o counseling his 38 y/o Mom and 57 y/o Grandmother.

Gma's problem is that she thinks Mom has been abusing painkillers and isnt in her right mind. She's watching as Mom has ruined her relationship with my sister (that's a different story) and now OB. She knows mom wont get herself help and she's scared Mom is gonna go down the same path as before. Shes also mad that Mom is continuously spreading lies about her to everyone and is making Gma look bad. But what Gma's most upset about is that Mom refuses to believe that both Mom and OB were in the wrong, and refuses to apologize. 
Mom is mad at OB, obviously, but Mom is more mad with Gma.
Mom believes that OB is completely at fault here, and she has no blame. She believes that Gma is taking OB's side on the whole situation. Mom has made it a "You're either with me or against me" situation and refuses to listen to anyone about it.

 I've talked to both Gma and Mom separately and both of them have budged very little on anything. Gma would at least listen to what I had to say and acknowledge my take on everything. She wouldnt budge, but at least she would listen. Anytime I tried to give my point of view to Mom, she would get mad and talk over me and tell me that "SHE wasnt in the wrong at all, and Fuck Gma and everyone else who helped OB. They can rot in hell". I know she was just being emotional at the time, but that's what she said.

I know that I should smooth everything out between Gma and Mom and hope that one day OB and Mom will forgive one another. I've done this multiple times and I'm honestly tired of it, I hate drama as it is. AITA for just leaving the situation alone?

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