Every visitor tells our 10 year old he's 'the big brother now' and has to set an example

Whenever relatives come over, someone ends up telling our elder son, very kindly, that he's the big brother now and must be good, help at home, not make noise near the baby. He nods and smiles. Then he goes to his room. He's always been a cheerful, chatty kid and I don't want this to become the main thing he hears about himself this year. My partner and I have started saying, 'He's already a great kid, he doesn't need a new job.' It comes out awkward, and the aunties look at us like we're spoiling him. How did you handle this with relatives without starting a family argument? ❤️