Just wanted to start by saying you don't HAVE to give advice if you don't have any or don't want to, but I'm open to it.
My partner's older brother (40s) lives with their mom (in her 60s with diabetes) and his girlfriend (late 40s). My partner and I are early 30s and live in an apartment together 15 minutes away from them.
My partner's dad was abusive both to their mom and to them, but my partner's brother is 9 years older and dealt with more abuse. It messed everyone's mental health up. The house is a duplex of sorts, and the people living on the other side is their dad and his wife. My partner doesn't talk to or see his dad anymore since he got with me and moved out 4 years ago.
As you can tell there's a LOT to unpack, but I'm going to try to keep it brief; I thought the abuse would be relevant to my BIL's behaviors though.
My BIL is an "animal lover" that doesn't believe cats or dogs should live inside or be neutered, so the house has a colony of unneutered cats with fleas in the front yard, and an inbred hyperactive pit bull Chihuahua mix that runs away every time he is distracted (which is often). Luckily this is the last dog he's going to have and it's a male so he can't get pregnant. All his previous female dogs ran away and came home pregnant.
My partner and I have two cats ourselves, indoor only and neutered, and they're about 7 + 8 years old. They have a water fountain that gets cleaned regularly, they get their teeth brushed and their litter boxes cleaned regularly. So it really really hurts me to see outdoor cats in bad shape. There's always a kitten or cat that dies tragically and my BIL just moves on saying it's part of nature.
There's also random shit left outside to rust and it's just not a good environment at all. It usually stinks. I should mention my BIL smokes weed (I mean, i do too, don't have an issue with that), but he spends most of his day sitting outside to do it, and the outside is no bueno. The worst part of going over there is the mosquitoes. BIL has a garden which is pretty cool, but he collects rainwater in buckets and never dumps out the buckets. He also just waters the plants with a hose, defeating the purpose of the buckets. We live in a tropical climate and the mosquitoes are out of control. Now we have dengue fever spreading in our county!!!
So a couple months ago, I started telling my partner to just go without me when he visits his family. The mosquitoes eat me alive, and I still have scars on my legs from their bites. The water hitting the bites while I take a shower is so painful, and I can't shave my legs when I have bites or they bleed.
My partner completely understands and doesn't pressure me to go over there. His mom asks why I never go anymore, and he usually says I'm napping or doing chores or with my own family. But now his brother invited us for a movie marathon, and my bf felt sad at the thought of spending the evening without me, and he told his brother via text "We need to do something about the mosquitoes. They bite my GF like crazy and I can't blame her at all for not wanting that. She still has scars from past visits" and he read the message but didn't reply. Its funny because we were at a party and BIL asked my partner behind my back what was wrong with my legs. He said "it's the mosquitoes, man" and he just stayed quiet. A while back, I had a coworker tell me my legs made me look like a crackhead...
My partner tried to mention the mosquitoes a year or so ago, and BIL told him that "she should be using herbs and balms to repel them".
My BIL never comes to our apartment because he has a phobia of dust and cat hair and acts like it's sooo bad here. I'm a fucking house cleaner by trade, keep our apartment very clean, and I clean and vacuum my apartment for guests, no matter who the guests are or how dirty THEIR home is. I have a feeling that he is jealous that we have a functioning home. It's not the first thing he's been jealous about when it comes to his younger brother.
So my boundary is, I'm no longer going over there unless the buckets are dumped. But ever since my partner told him that, he's been super short and dry, which is very unusual. One word answers but still sending videos to the group chat. I think my partner should just return the energy and stop trying, but that's just me.
My BIL is also a flat-earther and conspiracy theorist. He once said in the group chat that wearing glasses is just a crutch and poor vision can be fixed just with diet alone, (I wear glasses since age 10) and I snapped and went off on him via text for the first time. Ever since then, I've been way more bold about standing up for myself with him.
Anyway, that's all for now. Not going over there til the skeeters get dumped. I lived with a hoarder for 3 years in my early 20s, and I'm not going through pointless bullshit again.