Since Sabellian is basically one of the oldest black dragons, I like to think it would be fair to say he's probably had some kids of his own at some point and (somewhat) knows how to deal with hyper whelps
The Black Dragon brothers being a dysfunctional family mess
Also fuck you Blizzard, reality can be whatever I want it to be, fucking horns your Ebon
Wish Embers of Neltharion did a better job of showing these guys actually developing brotherly bonds rather than just having it happen right at the end of the story.