There was no way she could stop now, even if she wanted to, and she watched her son's eyes widen as her fingers reached the edge of her bikini bottoms...."Oh... Fuck..." she mumbled under bated breath, then her hand slipped over the material and climbed ever closer to her waiting mound. The sexual need to excite her son was driving her down a dark path. She wanted him to see her do this. To touch herself. To make him lust for her even more. But, just before her fingers touched her welcoming slit,. I sucked him hard, trying not to lose a drop of his juices. To my surprise, Mark became hard again; Tom took hours to become aroused again after we had had sex. Mark wanted to fuck me again, and I wanted him too, but I said, “Tom will be wondering what’s wrong and will come looking for me, I’ll see you in the Jacuzzi.” “Ok, no problem,” said Mark, “See you in a bit.” Tom was lying back, almost asleep, as I approached the Jacuzzi. I slid into the bubbling hot water next to. ’ ‘Not even for me?’ she giggled, ‘I could be VERY grateful….’ I knew that she was only being playful, not even really flirting with me, it was the way that we teased each other all the time… but…. her choice of words sent a tingle surging through my groin, Luci and Lulu had used those exact words and then shown me that they could be ‘Very Grateful’, both of them… separately and together! ‘How grateful?’ I played along. ‘Not THAT grateful, you randy sod,’ she laughed slapping at me playfully,. Are you ready for the challenge?”“Yes sir,” they said in unison.He brought over the paddle and started by warming up their backsides. He went back and forth, slowly building up the intensity on the four butt cheeks in front of him. Sometimes spending an unequal amount of time on one girl over the other. “Okay, one of you is going to take 5 strong spanks. Which is it going to be?”Sarah chimed in first, “Please let me have them Master. I will take them.” He moved behind her and gave her.