NTA, if I had nowhere to go and someone, family or not, offered me a place to crash on short notice, I'd be grateful for a flattened cardboard box to sleep on. Your nephew is 19 years old, I'm 30 with a bad back from working in a warehouse for a lot of my early twenties and then as a caregiver for people with disabilities and finally as a nurse, and just last winter I had nowhere to go (I have a home, but snow made it hard to travel) and a friend let me crash at her place. I slept on my jacket because she didn't have another mattress or a couch, and I was sore in the morning, but I would never complain to someone letting me crash on short notice.

Your nephew needs to grow up, your brother needs to stop being a hypocritical, bigoted ass, and your family needs to go screw themselves. 19 years old is not "just a kid," he needs to learn to not act like a spoiled child.