Duke Henry watched as Stella apologized to Hendrick when he turned utterly silent. Seeing his two children have a disagreement like that was a first.
Hendrick almost always just acquiesced to what Stella wanted; which he was trying to do right now but he had misunderstood her. She wasn't telling him to not marry Alina. She was just sulking that he didn't listen to her former warning.
Stella usually accommodated even her brother's obsessiveness. She only chided him gently when he was too much. It was surprising to see her get angry at her brother whom she had been able to tolerate for so long.
But then again, Stella was right to have scolded her brother. She had already told him not to choose Alina but he still did. And now, he was suddenly saying he changed his mind. It was unacceptable behavior.
He had already proposed to Alina and the lady finally accepted. Hendrick had to take responsibility for his actions.