What is the uncertainty about?

"... You would not perchance have any notion of who might have wished my brother ill, would you?" (Game of Thrones)

I'm sure this "might have" expresses uncertainty. But does it express that the speaker was uncertain whether anyone wished his brother ill or not? Or does it expresses the speaker knew definitely someone wished his brother ill, but he was uncertain if the bad guy was just wishing his brother ill or was planning to do something else to his brother? Or is the speaker uncertain about whether the bad guy wished his brother ill at all?

Thank you in advance.