He had expected to feel his sister's ass. She'd squeel and jump up and then maybe not hog more than half the couch. Instead his hand came down not on the outside of her skirt, but up it. Wait were those her panties? He wiggled his fingers and felt... That was her pussy!
His sister froze stock still and looked over at him. For a moment she thought that Tessa was going to slap him. Instead she moaned and began to grind against his hand.
What the fuck?! While his mind was blown, his cock gave a jump in his pants. Pussy. It had been too long since he'd gotten laid and his sister was letting him, no she was encouraging him, to finger her fanny. He didn't need any more encouragement than that. He started stroking her slit through her panties and she clearly wasn't objecting. She spread her legs a little which gave him easier access. He rubbed again. Yes, that was her cleft. He stroked up and down, or his finger was right near the top. She was letting him stroke her clit. Fuck, that was hot. His cock started straining at his pants. Luckily Mum and Dad were focused on the telly, so no worries. He kept stroking his finger up. Tessa clearly wanted it because she was grinding against him, breathing hard, and making little moaning sounds when he hit her nubbin. Her panties were also getting wet.
When she threw a blanket over them and told him to stick a finger in, he didn't have to be told twice. With a little wriggling he slipped his fingers inside her damp panties and into her slit. He stroked her up and down her slit mostly to get his fingers wet and then went straight for her clit. When he did this with Megan, he normally used his tongue. They'd left petting behind. He worked her clit, rubbing, pinching, flicking. She also asked him to stick his fingers in, so he alternated rubbing her clitty with finger fucking her. Apparently she didn't have a cherry, because he would have popped it by now.
He glanced back over to Mum and Dad. They were clueless. Then again Dad was always clueless. Mum seemed lost in the movie. He leaned in to his sister to whisper in her ear. "You like that do you? You're drenched. Can you cum quietly, or are you going to squeal and give us away?"
Damn his cock was hard. He missed getting laid so much. If Tessa was this horny, he'd have to fuck her once everyone was asleep.