Sister In Law Arrested For Embezzlement - Brother Can't Work - How Do I Help?

I recently found out my sister in law has been arrested for embezzlement. Her sentencing is in April. It was ALOT of money (over a million). She's looking at a maximum 20 years, although it appears she accepted a plea deal, so she's probably going to do 3-5.

She's been the sole breadwinner/taking care of my brother, who has a number of mental illnesses (bipolar/depression/ADHD/OCD). He also had a massive car accident several years ago resulting in a TBI. He cannot work and I don't think he's on disability (but he definitely should be).

I found out about the embezzlement charges from a friend of a friend, confirmed it (it's literally been in the news) so they don't know that I know. I'm actually scared she hasn't even told my brother. She's hid a ton of stuff from our family for years.

I'm worried that once she goes to jail, my brother won't have anywhere to go. My mom can't take him in, and even though technically I "could", it would severely affect my life. I'm trying to build something with my girlfriend, I'm planning on asking her to marry me soon, and having him in the house/taking care of him would severely test that relationship. I can't risk him being manic in my house, and things are going REALLY WELL with my girlfriend and I and I'm terrified having him here will blow it up.

My question is - What's the best route to go here? I feel like it might not be my place to say anything to my brother about my sister in law in the case that if he doesn't know, he'll go ridiculously manic. I'm scared to outright tell my sister in law that I know about it and ask her what her plan is for my brother. But I feel like I should do something. My fear is that once she is sentenced in April, my brother will be out of a place to live very quickly. I spoke at length with my mom last night about this, and for now we've said we'll do a wait and see approach, but April will be here before we know it, so I feel like we should do something. I just have no idea what that is. Any advice would be super helpful here.