Jeff set it so he would have two penises.
When he peed, he'd pee through both of them simultaneously. They could each be aroused separately or together. Also, they were each bigger than an average penis (of course).
A few months later, he'd hinted at it here and there—not flaunting it, but making sure a few people noticed. And the rumors started spreading.
Even his parents heard the rumors.
"Jeff, we love you, honey. People have been talking. Is there something... strange going on with your private parts?"
Jeff laughed. "How did you not notice that I was born with two penises?" He pulled his pants down to show them.
"Jeff, honey...." His mother and father stared in disbelief. "How could we not have noticed?" his mother said to his father.
"Who cares?" said Jeff cheerfully. He pulled his pants up. "I always thought everyone has two eyes, two nostrils, two arms, two legs, two testicles, two penises. Don't we have two of almost everything? Just one tongue, I guess. But two of almost everything."
"Yes, Jeff, but one penis, just one penis..." his father muttered uncomfortably, staring at the floor. His father was embarrassed that his idiot son had twice as many penises as he did.
"Yeah, I get it now!" Jeff was still smiling. "Regular people have one penis, one testicle. I'm just the lucky person who has two of each!"
His mother and father were both beet-red with embarrassment.
"No, son, normal people..." his dad nuttered. "Normal people have one penis, two testicles."
Jeff pretended to be shocked. "One penis, two testicles? That's so weird. Why not two of both?" he said, still smiling.
Jeff's mother was annoyed at his father. "Normal people? Penis, testicles?" she glared at him, shoving an elbow at him.
"Oh, right," his father said, even more uncomfortable now. "It's also normal for some people to be... to be 'women', and they have no penis, and no testicles."
"Very smartly said!" Jeff's mother snapped, rolling her eyes. "Yes, Jeff, some normal people don't have any penises or any testicles. Your wise father has just determined this."