My two daughters were having a discussion about family resemblance. 

"I look like Mom," said my nine-year-old, "but I have Dad's eyes and Dad's lips."

The six-year-old said, "And I look just like Dad, but I have light hair."

Then she turned to me. "Mom," she asked, "what does Dad have to do with us being born anyway?"

Her older sister jumped right in.  "Don't be stupid, Christina.  Dad is the one who drove Mom to the hospital."