My brother cut off all contact with our family except to send "wake up" messages

My older brother (34M) used to be the most grounded person I knew. Steady job, great with his kids, always the one talking everyone else down during family drama. Somewhere around 2021 that started slipping.

At first it was just him being quieter at holidays, distracted. Then he started sending long texts to the family group chat, usually late at night, about things he'd "researched" that we needed to know. When people pushed back or asked questions, he got defensive fast, then eventually just stopped responding to anything that wasn't related to his messages.

He missed our dad's 70th birthday in the spring. Didn't call, didn't explain, just sent another one of these texts a few days later like nothing happened. My sister-in-law told my mom privately that things have been rough at home too, but she's staying out of it for the kids' sake.

I keep drafting replies to his texts and deleting them. Part of me wants to engage, ask him real questions, see if there's a way in. Part of me is just tired and doesn't want to get pulled into something that goes nowhere. My mom cries about it more than she lets on.

Has anyone found a way to stay connected without it turning into a wall of silence or a fight? I miss my brother. I just don't know who I'm talking to anymore when he does respond.