As Malo was speaking English to Melchior, I decided to continue in English.
Malo and Melchior were noisy in the stairs while Marine was giving a course downstairs. I asked both of them to be quiet but they did not. See what happened next:
Pierre: "Oh, shut up!"
Melchior: "Daddy, what did you say?"
Pierre: "Shut up!"
Melchior: "that's rude"...