Jacob had followed her down and until this moment had been enthralled in what he was seeing. He watch as his slutty little aunt grinded her wet cunt onto her own fathers cock and it served to get him even harder than he had been before. Needless to say, he wanted to play. He walked up to the incestuous pair and smiled at his Grandfather. "She looks good at that" He said, a grin still on his face. He got on his knees behind her and wrapped his hands around her body, grabbing and playing with her tits, squeezing them and gently pinching the nipples, enjoying the feel of her naked skin, his hard cock grinding against her ass.