How Can I Support My Little Brother Through His Trauma?

So most of my emotional trauma comes from the way my dad treated me as a kid. I’m on vacation with him and that whole side of the family right now, and yesterday we had to listen to him yell at my little brother about how he couldn’t decide what to eat, then about how he wandered off and was treating everyone like dirt (he wasn’t), and he even made him apologize to each of us individually, despite the fact that he was clearly the only one who was angry. It felt almost like it was me being yelled at, and I felt disgusted when my brother was forced to apologize to me—I couldn’t even look him in the eye. I want to say something to him privately to let him know I’m there for him if he needs someone to talk to, but I’m still dealing with my own trauma and I’m scared of the potential repercussions from dad if he found out I’d reached out like that. I just remember how alone I felt when I had to deal with that, and I don’t want him to feel like that too. What should I do?