Ooh hoo, Degas wasn't mad before, but faced with Athanar repeatedly saying he's a spoiled kid with misplaced anger, he'll be mad fast.
Especially since his concerns have absolutely nothing to do with the practical running of the mead hall or of who is in charge of what. He just cares that his sister married a lord and received an inheritance with that, and it has been taken back through no fault of her own, and she's got an heir brewing inside her. Degas just wants to make sure his nephew (he's assuming it's gonna be a boy, whether or not he's right) gets his birthright.