Question

what was the Nicholas reaction to his brother demand

Answer 1

nicholas did not like the way his younger brother jacopo asked the narrator to drive them to poleta on the coming sunday.he glared at jacopo in anger and expressed as if he was annoyed. It was because nicholas cares a lot about his self respect he did not want any kind of sympathy or help from anyone.
also he did not want to disclose about their sisters illness and now there was a chance of their secret to be spilled out.
so he was annoyed of jacopo asking the narrator to drive them to poleta.

hope it helps.