On some level, the Doctor is aware that it's not his business and Wrathion doesn't owe him more explanation, but that's never stopped him before. He could sympathize openly to a certain extent, perhaps, though how much he chooses to share of his own losses is always variable.

"I know a bit about that. Not the brother part. Well, I did once." The tips of his fingers skirt along the edge of the table for a moment. If they're sharing, well...he should share, too. He should. He's not always good at that, either, and only in certain moments. But if ever there was a time. "They're gone. I understand that, and I'm sorry."

In what way does he understand? He doesn't elaborate. It's definitely not important or anything.

"What you are, what you've shared, I don't take it lightly. Your secret is protected, and you'll be protected if I have anything to say about it. And I do have quite a lot to say, generally, as you well know."