[... why is it so familiar now to see a father deny his son? Of course, this isn't the same situation as her brother. She doesn't know who this person is, but she can't very well act as if she didn't see anything]

I... wish I knew what to say. I'm really sorry for seeing this. It's none of my business.

But um...! Please... please don't think any of that was your fault. I doubt it means much now but...