Guess the Game Name

A boy was assigned a paper on childbirth and asked his parents, "How was I born?"
"Well honey..." said the slightly prudish parent. "The stork brought you to us."
"Ohh..." said the boy. "Well, how did you and daddy get born?" he asked.
"Oh, your grandparents found us under a rock."
"Well how were grandpa and grandma born?" he persisted.
"Well darling, they were found under a cabbage leaf," said the parent.
Several days later, the boy handed in his paper to the teacher who read with confusion the opening sentence: "This report has been very difficult to write due to the fact that there hasn't been a natural childbirth in my family for three generations."