One day, a kid walks in on his brother and his girlfriend having sex.

He
says, "What are you doing?" and his brother replies, "I'm playing poker
-- she's the queen and I'm the king."

The kid leaves, not knowing any better.

About a week later, the boy walks in on his parents having sex and says, "Dad, what are you doing?" and his father replies, "I'm playing poker --
she's the queen and I'm the king. "

He leaves again, not knowing any better.
The next day, the boy's brother walks in on him masturbating and says, "What are you doing?" and the kid says, "I'm playing poker"

"Where's the queen?" his brother asks, and
the kid replies, "Why do I need a queen when I've got a hand like this?"