What should I do?

My brother and mother have a strain relationship and it's def making things awkward between fam members... Their arguments can be summarised to this:

>Mom asked bro to do stuff
>Bro didn't do it within acceptable time limits
>Mom berated bro, continue talking and talking till the conversation turned into something else entirely
> Bro got frustrated, he either ignored her or talk back
>Everyone mad, returned to their room and pretend like nothing happened

We've been in this loop for awhile now...eventually, my lil bro shut us out. The amount of relief and happiness I felt when we talked like normal siblings were alarming to say the least. I get it that we've already have chores schedules and he should take responsibility but my god the things my mom said... Genuinely fucked up sometimes, got me questioning if she actually love us or not..

I get that she's fed up raising us like a single mother, but I wish she didn't use us as emotional outlet.. I'm worried about my brother's mental health but I also want him to understand that he can't just ignored important chores like taking care of his own cat.. I don't think he's gonna listen to me either, pushing this topic might actually make everything worse but I'm the only mediator at home. What can I do to make him open up? Any advice is appreciated