Surprised, the dad answers, "Well, sure, son, we wouldn't be normal ¹ if we didn't. There are all kinds of breasts...depending on a woman's age.
In her twenties, a woman's breasts are like melons, round and firm.
In her thirties to forties, they are like pears, still nice, but hanging a bit. After fifty, they are like onions."
"Yeah, you see them and they make you cry."
Not to be outdone, the daughter asks their mother, "Mom, how many kind of boy thingies are there?"
The mother, delighted to have equal time, answers, "Well, daughter, a man goes through three phases.
In a man's twenties,a "mans" boy thingie is like an oak, mighty and hard.
In his thirties and forties, it is like a birch, flexible but reliable.... after his fifties, it is like a Christmas tree."
"A Christmas tree?"
"Yep, dried up, and the balls are only there for decoration."
¹ Italics are mine.