Dad and Mum answers to their kids on sex education

A family is at the dinner table. The son asks his father, "Dad, how many kinds of boobs are there?"
The father, surprised, answers, "Well, son, there are three kinds of boobs. In her 20s, a woman's are like melons, round and firm. In her 30s, 40s and 50's they are like pears, still nice but hanging a bit. After 60, they are like onions."
"Onions?"
"Yes, you see them and they make you cry."
This infuriated his wife and daughter so the daughter said, "Mum, how many kinds of "willies" are there?"
The mother, surprised, smiles and answers, "Well, dear, a man goes through three phases. In his 20's, his willy is like an oak tree, mighty and hard. In his 30s, 40s and 50's it is like a birch, flexible but reliable. After his 60s, it is like a Christmas tree."
"A Christmas tree?"
"Yes. The tree is dead, and the balls are just for decoration."