AITAH for not picking up the slack and hating my disabled roommate and her brother?

My boyfriend (25M) and I (22F) moved in with his childhood best friends, we'll call them kassidy (30F) and tanner (26M) about 2 months ago. We are renting a two story home in which my boyfriend and I get a bedroom and a small loft upstairs to ourselves while the rest of the home is communal (not including bedrooms.) Kassidy and tanner are siblings and kassidy has an undiagnosed disability that puts her in pretty significant pain throughout most days which causes her to be unemployed.

I assumed that Kassidy's disability would hinder her ability to do chores and originally had no problem picking up what she couldn't handle throughout the day.

The issues started immediately once moving in when they started declaring the house as "theirs" and making rules for my boyfriend and I that only apply to us without talking to us first. I mean things like "you're not allowed to go on small grocery trips, only big ones" and "If you buy food you have to make sure everyone gets equal amounts even if you bought it." Yet they constantly go on small grocery trips and buy things just for themselves. They think this is okay because we are renting a home owned by one of their family members and they plan on living in it "for the rest of their lives."

(We also can't use the communal living room because it's full of cans and the TV is on for their dogs so we can't change it)

They also don't clean up after themselves but expect my boyfriend and I to leave every area spotless. Ex. One pot in the sink from us is enough for a whole conversation but they have ~$500 worth of alcohol cans in bags on the back porch that you're not allowed to tell them to get rid of because they will "get to it"

Kassidy will do chores to the point of physically hurting herself and then Tanner will get mad at my boyfriend and I for "not stepping in and stopping her" but if we go ask to help her, she gets defensive and won't accept help.

They have two large breed dogs while we have two indoor cats. They do not walk nor train their dogs and will let them out max twice a day for 5 or so minutes at a time. They allow their dogs to chase and bark at our cats and we are not allowed to discipline or otherwise scold their dogs because it's "not our job" so we have to endure while their massive dogs jump, bite, and scratch us.

We are not perfect roommates. We forget laundry in the washing machine and don't always do dishes right after making food but any time it's pointed out to us, we apologize and do what needs to be done. Yesterday I bit the bullet and cleaned the fridge that was full of their mouldy leftovers and confronted them about it only for them to say they weren't their leftovers and it's not their fault.

We live in a very expensive place in our country and living with them keeps our rent and expenses extremely low so I'm looking for advice on how to maybe make them better or bear through it?