Convince him to join Emily and James

"I'm going to suck your cock," you say, lowering yourself to your knees. "And I'm going to tell you about how much Emily likes to get peeks at her brothers when they're naked." Technically, Emily had only mentioned looking at James, not Peter. But you figure that if she's willing to perv on one little brother, then she'll be willing to perv on the other, and you've already gotten the ball rolling.

Peter looks confused but happy. You're on your knees in front of him, playing with his cock in your hand idly as if it were a pen. You smile up at him somewhat innocently. "I was talking to your sister," you explain. "She and I have been having some fun together today. The same kind you and I are going to have. After we were done, she told me that she likes looking at you two. When you're naked. She told me about your nice dicks." You lick the tip of Peter's head and he groans. You can taste his precum, as well as the remnants of what was probably an orgasm less than an hour ago. "I think it's hot, that she looks at the two of you. I like looking at the two of you. I like playing with you like I am right now." You sink your head lower, pushing yourself to take more of his cock down your throat. You can feel him twitching already. The shock plus the recent orgasm you taste on the tip of his dick likely makes your job especially easy for you.

"Do you like my ass?" you say, wiggling it in the air behind you. "Some guys tell me it's my best feature."

"F... fuck," Peter gasps, torn between staring at your ass and your face.

"Yeah," you say. "You want to cum down my throat?"

"Yes!" Peter says.

"Good," you say. You take his cockhead all the way into the back of your throat, making quiet gagging sounds and pushing your face against his stomach. You can feel his balls against your chin, feel them shudder as cum shoots up his shaft, out his tip, down your throat and into your stomach.

You pop up onto your feet seconds after you take his load, leaving it still dripping with a little bit of cum. "Great!" you say with a friendly smile. "Think about what I said. I'll talk to you soon!"

You grab your clothes again and skip back to Emily's room.