AIO for wanting to kick my brother in law out over a cat

I live with my girlfriend Jane (25) and her brother Brady (23). We moved in 2 years ago. They have 3 cats between them. I have asthma and a cat allergy so as u can imagine, I have some breathing problems on occasion specifically when sleeping. I was aware of the cats before I moved in so this was all voluntary, but I was not prepared for the intense exposure therapy.

I smoke weed (I’m a stupid asthmatic stoner ik) and vaped for a few years. Last year I stopped because I went to the hospital for an asthma attack brought on by vaping. I’ve been off nicotine for a little while now and try to stick to edibles as to not bring on any more unnecessary asthma attacks.

Brady works as veterinarians assistant and constantly sends videos of cute animals in the roommates group chat. A week and half ago Brady sent us this adorable kitten, asking if he could bring it home. I responded saying I don’t think my asthma could take 4 animals, and how my quality of life could already be better. I have gotten a tolerance to the cats but not enough for another.

At first his responses were reasonable saying how it must suck to have allergies and how I could go to an allergist and get shots. But slowly it devolved into him getting mad that I was not budging on the idea. I was at work when this convo was happening, and my break ended so I stopped responding. My girlfriend was responding for me basically saying how even if I got shots and went to the doctor etc, that it would be my choice and Brady couldn’t force me to do anything simply because he wanted the cat. Here is one of the messages Brady sent in the gc verbatim:

“i just don’t want all of ours needs and wants to be affected by one person when they can go find other alternatives yk. same as i wouldn’t want to hold you guys back from ur wants and needs if it was the other way around”

When I read this message I was kinda stunned. Like, I’m sorry my breathing irregularities fucked with your desire to have a 4th cat my guy. The messages keep going while I’m at work and it eventually gets to the point where Brady is saying I should just go to an allergist and how I’m stopping everyone from getting what they want because of my allergies. Another message from the gc verbatim:

“ i’m not saying i don’t understand all these problems but tbh yall are being babied rn or at least it feels like that to me. OP needs to start taking those immune system pills and oil that yall have for him daily. these are all things that again are one person affecting everyone else.”

We keep shutting the idea down until he eventually gets mad enough to tell both of us to shut the fuck up, and says I’m “blocked bc ur annoying” and how we ambushed him at work (he brought up the cat we were just responding). He says we’re being aggressive even tho we were calmly stating why even if I “should” get allergy shots, the closest allergists to me do not take my insurance. And either way it’s my decision to pay out of pocket for that medication if I did want to do it anyways. Jane had enough and left the gc and he calls her a pussy….in the gc she can’t see anymore lol.

Yesterday Jane went to go put some cash on Brady’s nightstand because she owed him money, and he wasn’t talking to us so she figured just leave it in the room. When she opened the door I heard a meow. Yup. The kitten was in the room. He had left for work and just locked the kitten in his room all day, trying to hide it from us.

We really don’t know what to do about this situation, considering Brady also has some bad anger issues and has done violent things in the past. He blows up over small disagreements and my gf does not feel comfortable arguing with him in person. He’s not technically on the lease so we’re thinking about calling the landlord but we aren’t sure. This is honestly the straw that broke the camels stupid fucking hump, so the cat isn’t the only reason we’d be asking him to leave. But that’s a story for another time. He just doesn’t respect me or Jane. And he does what he wants without regard for others. He also talked shit on his IG story that we still can see, and invited people over without warning (it’s a house rule to give as much notice as possible when having people over) He’s just been disrespectful all week. We’re kinda stuck here and don’t know how to move forward. Advice appreciated.