My mom fosters two distant cousins. They help at her store. One is a teenager, and the other a young adult (let's call him Ander)

I came in last week, having not been home since December. Yesterday, I'm helping supervise body work on mom's car and mom joins me there in the evening. It starts to get late and she wants to relay instructions for the boys to close up shop but she doesn't have Ander's phone number, so she calls her neighbour to give his phone to Ander. He obliges but moments later he calls, pissed, that he didn't sign up to be insulted. Mum immediately says to give the phone to the teenager. She proceeds to give instructions and end the call and completely glosses over the "insult" statement by her neighbour. So I ask her. Turns out Ander has done this before, amongst other public shows of disrespect towards my mother

When we get home, against my mom's wishes to ignore his affront, I confront Ander and he keeps being rude towards me and my mom. This devolves to a fist fight and afterwards I ask him to pack up and leave our house. 

He obliges, saying how he's done with my shit. Starts to pack. Says he would treat my fuck up. Says I'll pay for disrespecting him in such a manner. How do I have the guts to hit him. Is he a kid?

I can't believe it. He's been with us over 5 years now. My mom has treated you like her own son. Clothe you. Feed you. Sheltered you. Bought you a phone last Christmas and you disregarded it because its too small. It was an itel. I'm barely ever home myself. I expect that when I'm not home, you'd protect and stand up for my mother not disrespect her.

Turns out his reason for not picking the call was because, in his words, Why would mummy call &lt;neighbour&gt; when I have a phone in my pocket?

In the meanwhile, my mom is now on the phone with my aunt, and his dad. She's begging me to let him stay but I'm not having it so she figures they'd be able to talk me down.

Now the extended family is involved. Most of them saying the same thing, that I should let him stay and we should all go to bed and discuss it in the morning. But I have a better idea, since he wants to leave, and I don't want him here. I escort him and his stuff to another aunts place, a few blocks from my mom's.

This morning, mom agrees to have him back, at least till he can start a business of his own with her help (which was agreed upon when she started fostering him, estimated to be the end of this year). I want whatever mom wants but I'm not comfortable with it. Dad (not around) and siblings and a few cousins agrees with me that he should leave. My aunt gives him a stern talking to and promises me that he would do better 

Ander returns to the store. We share a terse but civil interaction. No apology was offered to me or my mother

A family meeting is planned for this evening.

TL;DR cousin is disrespectful and I kick him out in the middle of the night, starting a shitstorm of family drama