Allison (b).

"Oh, Uncle James!" Allison covers herself reflexively, and you stumble backwards, catching yourself on the sink.
"Allison....honey I'm sorry...I was expecting Jenna..." You feast your eyes on her nubile body. You think back to the previous day, and what you've already done with her...and Riley.
Her cheeks are red with blushing and she looks down. "I'm sorry...I just...I wanted to take advantage of the empty house to use your nice shower..."
"Where's Riley?" You can't tear your eyes away, and her eyes are studying your body, too.
"She went out to get us stuff to make for dinner. You're going out with Mom and Dad, right?" She unconsciously licks her lips. You realize that you're as hard as a towel rod, and you grab a towel to cover yourself.
"Yes."
"You don't have to cover up, Uncle James..." she chews on a fingertip like the teenage girl that she is. "I mean...after what we did..."
"You need to keep that to yourself, honey."
"I'm not going to tell anyone, silly." She giggles. "Why would I?" She steps from the shower, water dripping from her body. She pulls the towel away. "You're all... stiff, Uncle James." She grabs your dick, taking in a shuddering breath. "Can I help you... take care of that?"
"I don't know if that's a good idea, Alli...." you bite your lip as she rubs your shaft with her thumbs.
"But I didn't get a chance to thank you yet...for helping me..." she rubs a little faster.
"Uhhh.....Alli..." you moan, betraying your own words. She's a tempting little cat: barely 18 and already a tempting little nymph.
"Just..." she sinks to her knees. "Just relax... let me...." she kisses the head, "help you out."
Which is how you find yourself sitting on your closed toilet, leaning back against the tank, as your teenage niece slobbers on your cock, fighting to get it into her tiny throat as you hold her wet hair with your hand. She gives you frequent flashes of those pale blues, smiling around your fat cock like the Cheshire cat.
"Careful... don't hurt yourself." She makes alarming noises as she attempts to fit your whole dick in her tiny mouth and down her gullet. "Breathe..."
"I'm okay..." she rubs with both thumbs up and down your slick shaft. You throw your head back and groan in pleasure.
"Will you fuck me, Uncle James? I still need practice..." she goes on her hands and knees on the bathmat, wiggling her butt in the air. How can you resist that?
"Fuck... I'm going to get in so much trouble..." you mumble as you kneel behind her.