Responses
I think it is the brother. He was practicing black magic, he may have survived. I also think he knows that Jannette is her daughter that is why he is talking to Lord Alpheus and supporting him maybe.
It was said that Jeanette is the result of the brother's experiment with black magic before he 'died' hence Lucas said that she's a chimera.
That black haired man on the roof has uncanny resemblance to the emperor's brother. Mystery, mystery~