Man v Woman

A family is eating Christmas dinner and the son asks his dad how many kinds of boobs there are, Dad says;

"Son a woman goes through three phases, in her 20's, they're like melons, round and firm, in her 30's to 40's, they're like pears, still nice, but hang a bit."
" After 50 their like onions?" the boy says,
"Yes" dad says "You see them and they make you cry."

This angers the wife and daughter, so the girl asks "How many types of willies are there?"
Mum says "a man goes through 3 phases as well, in his 20's it's like an oak tree, mighty and hard. In his 30's and 40's, it's like a birch tree, flexible but reliable. After 50 it's like a Christmas tree."
"Why" the girl asks
Mum says "its dead from the root up and the balls are just for decoration."

@GRIMMY