Just for Laugh - "Happy Family"

A man from the census bureau was doing a door-to-door survey.
A little boy answered the door & said his family wasn't at home.
"Nevertheless, can I have your father's name?" asked the census man.
"My father's name is Laughing," answered the boy.
The census man was surprised, but he pressed on.
"And your mother's name?" "Her name is Smiling," the boy replied.
"Wait a minute little boy! Are you Kidding?" said the census man.
"No, that's my sister," the boy answered.
"I am Joking."

If it is funny, pls comment. Thank you