Sometimes Sherlock sucked his thumb, and for the most part John thought it was weird. Sherlock didn't do it often, just when he was really, really tired. He'd sleep on his side and let his thumb slip into his mouth, his face resting on his palm. Sometimes it was kind of cute, John thought.

Sometimes John would think it was entirely weird. He knew it wasn't normal for a 35-year-old man to suck his thumb. But then he thought hardly anything about Sherlock was normal. Everything went back to something strange in Sherlock's childhood, even thought Sherlock would claim he had an entirely normal childhood.

Sometimes John would think it was…sexy. Is that the word he liked to use? He wasn't proud of it, he would never tell Sherlock. He would never tell Sherlock that when John couldn't sleep, he'd listen to Sherlock sucking away at his fingers and imagine Sherlock sucking away at something else. He would never tell Sherlock how tempted he was to give Sherlock something else to suck away at.

But he never did. He'd lay there and listen to Sherlock suck, imagining Sherlock sucking, and stroking at himself.

He didn't like it. He thought it was weird, this whole situation. Sometimes he'd think too much at what he was doing, so he'd stop. And Sherlock would stop sucking, and everything was normal. But then Sherlock would begin sucking again and he would start again, too.

In the morning, John would wake up sort of ashamed. He knew it was weird. He knew he should try to steer Sherlock away from every once in a while sucking his thumb. But he couldn't do it.

"How did you sleep?" John would ask.

"Perfect, I haven't slept that well in a while." Sherlock would yawn. "You couldn't sleep, then?"

"How did you know?" John would be sort of scared, as if Sherlock knew what he did and why he did it.

"You're barely waking up when I'm waking up. You should've been up hours ago."

"Oh, you're right."

"Is there something else? You're acting strange."

"Nothing else," John half smiled, "I assure you."

"You know I'll figure it out if there's something else, right?"

"I do know that, Sherlock."

Three weeks later, it happened again. The exact same thing. And again, John was not proud.

The same morning conversation happened, and again Sherlock was questioning if John was all right. John assured Sherlock he was.

The next day, Sherlock figured it out.

"John," Sherlock said at lunch, "Do you masturbate when I suck my thumb?"

John was completely caught off guard, "I-uh-what?"

"You heard me."

John cleared his throat, "I don't know what you're talking about."

"I won't think it's weird, John. I suck my thumb, after all."

"I-uhm. No, Sherlock. I was asleep."

"No, you weren't. You woke up at the same time I did, you were awake."

"So?"

"And you touched yourself."

"Why do you think that?"

"You didn't try to have sex with me this morning."

"So?"

"You never do when you did the night before."

Silence.

A lot of silence.

Awkward silence.

John felt weird. Like it was wrong, like he shouldn't be turned on when Sherlock sucks his thumb -which he shouldn't be. And he felt weird now that Sherlock knew -like it was a secret. And he felt weird that he would masturbate with Sherlock right next to him -it's not like Sherlock never does that to him.

"You don't have to feel weird, John."

"Why?"

"It's natural."

"But-"

Sherlock began to laugh. John's cheeks went red because Sherlock was laughing at him. He began to feel angry. He got up from the kitchen table and stormed away.

"No, John, wait!" Sherlock went after John.

John slammed the door on Sherlock's face, but Sherlock opened it quickly. "Go away, Sherlock. You've embarrassed me."

"I, the grown man that sucks his thumb, has embarrassed you, the grown man that masturbates?"

"I…do it to you sucking your thumb. That's weird, Sherlock."

"So?"

"So, it's weird and you've embarrassed me."

Sherlock put his arms around John. "It's all right, John. I give you permission."

"Permission? I don't need your permission."

"I know, you were doing just fine without it."

Sherlock began to laugh again. This time, John laughed too. They laughed together for a few minutes, then they stopped.

"I'm sorry, Sherlock."

"Don't be silly, John. You don't need to be sorry."

And they continued their every-once-in-while traditions of sucking and touching, but not each other.