How it works in my house:
"Son, do your chores please."
"Yes, sir."
Done.
replies(5):
"Son, do your chores please."
"Yes, sir."
Done.
It is plainly offensive to address kin as "sir".
If your children respond to orders like trained animals or soldiers, they are doing so because they were conditioned to do so. I am choosing to define that conditioning as abusive because it simply doesn't happen naturally.