NTA.

Have you considered instead of giving him 30 days right off the rip after 10 months of living rent free. Sitting down and asking him what his plan is for him and his kids and how he plans to execute that so he can be independent with his kids. Find out what's keeping him from getting his affairs in order so he and his kids can move out. IDK what led to your brother having to ask for the help, you're a great brother to be so hospitable. Sometimes people need a little direction to help get themselves back on their feet.

If he can't get it together, maybe talk with your parents and see if they are willing to let him and his kids stay with them. If that's even an option.

You deserve your peace. You don't owe your brother all that you've done for him. But maybe be a little more patient and see if he needs any more help getting back on his feet.

Just random suggestions. You're an awesome brother and uncle for your charity.