AITA for reminding my brother he chose his son's therapist and he needs to stop blaming me when I'm helping him?

My 13 year old nephew came to live with me in December. This is a temporary but we're not sure how long he'll be here arrangement. My husband and I will keep him for as long as it takes. But I'll be honest I could see him staying for years.

The reason he's here is because he's full of anger about his dad, who's my older brother, got remarried 18 months ago and my nephew has felt like his dad's stepkids get more of his time, attention and love than him and it has turned into hatred for his stepsiblings (5 and 6) and in December he unleashed all that anger on the kids and yelled at them. He told them he hated them, he wished they'd die so he could have his dad back and any number of things. My brother had taken his focus off his son a lot after remarrying and was shocked by the outburst and calming my nephew down took hours because he yelled at his dad when he was finished yelling at the kids. My SIL attempted to step in but my nephew yelled at her and then went back to yelling at his dad. It was the first time my brother realized his son was angry.

I hadn't seen them since my brother's wedding but it was a big change. My nephew had mixed emotions on the day of the wedding and we talked about it but he wasn't angry. But in the months that followed that anger became a concern and my brother didn't see it.

After talking to my nephew when he was "calmer" he realized more outbursts were going to happen. Which led him to reaching out and asking me if my husband and I could let my nephew stay for a while. He was honest that he didn't know how long but he didn't want to send his stepkids packing and didn't want my nephew to feel like this was the end of the marriage and it would be back to just the two of them so he didn't want to move out with him. I told him assuming he arranged for therapy and everything else that was fine. My brother sends a weekly amount to cover expenses for my nephew.

My brother set up a therapist for him where I live (we're a couple of hours from each other) and my nephew is doing school virtually right now. My brother drives out to see him once a week and joins him for therapy some weeks. But he's not happy with what the therapist is saying.

He confronted me on it and was trying to blame me for the choice of therapist and because therapy wasn't a quick fix. He told me what good is it doing if he's here and with a therapist and we're not helping. He asked what sort of therapist I was bringing him to. Those were the kinds of comments. I reminded him he chose the therapist and I was helping him so he needed to stop blaming me. My brother told me there wasn't another option as much as others might disagree. Which makes me think the therapist suggested something he disagreed with.

But my brother left angry and he called me a couple of days later and told me I don't need to turn on him when he doesn't have a fucking clue what to do and he's still coming to terms with the fact his son hates him and hates innocent kids who did nothing wrong.

AITA?