Tod gasped, and it wasn't from the more than comfortable weight pressing down on his crotch. Brother and sister weighed the same, but more, they were the same. Kelly's rectum felt exactly the same, hot and slick. She pushed down, sighing, and then drew a deep breath and held it. Her entire body shuddered, and Tod felt the vibration transferred through his rod. He gasped too, but then the girl settled down, reclining and relaxing against Tod. She raised her head and smiled at her brother.
"...so stiff..."
"Yes, I know!"
"...all the way deep inside me...."
"..mmmm...."
Tod wanted to fuck her, to take her, to use her and cum inside her. He wished he had full mobility so he could do something like that, and not simply sit with her engulfing him so totally. But it was a good alternate. He glanced at the boy; Andrew was a great alternate too. Each of them was. They seemed to bring into Tod's life, the missing feminine element that he had so badly missed. The room seemed to glow with it, with the gentle, quiet warmth of their passion, and what made Tod smile even more to himself, was the fact that this passion was also directed at him to some degree.
Then he watched as the brother placed his hand gently on his sister's ankle and run it down over her pointing foot. She raised her leg slightly and he pulled her foot over close and kissed it, and the sight of that one act made Tod's dick surge up hard within its confines. He rolled his pelvis downward, then up, making his dick move an inch either way inside her. She gasped, her body shivered again. Tod slipped both hands over her silken shoulders and kneaded her breasts. She put her hands over his and pulled them more firmly to her, and then both her legs went straight out - Andrew letting go quickly - and her feet pointed. Her legs strained, every muscle showing through her delicate skin. She moaned, and Tod could feel her rectum tightening around him. It squeezed, fluttered open and then rippled all along its length. He felt it; it was like it was jerking him off inside, and the next moment, gazing at Andrew's beautiful face and shoulders, fondling Kelly's tits, Tod came in the girl's ass; grunting, pushing upward, gasping. There was so much jiz coming out that the pressure of it squeezing out his hole actually hurt. He pulled down and rolled up and Kelly cried out softly. Her brother grasped her flailing hand and held it tight as her body jerked and twitched, just as Tod's was.
When the storm had passed, Kelly sighed happily and started to get off Tod's lap. Tod's cock slipped out of her easily, and it was instantly coated by a glob of his own semen which drained out of Kelly's well stretched hole. She stood, helped by her brother, and then the two of them came and knelt on the floor at Tod's knees, hugging themselves to him with eyes closed and happy smiles on their faces.
Tod closed his eyes and passed out right there in his chair; the satisfaction and contentment overwhelming and so long overdue that it all felt new and fresh.
Those first few days turned into a week, then two. A month went by and the twins never seemed to want to leave or even mention anything about it. After that amount of time Tod was surprised that he hadn't grown weary of them or tired or even bored, but there was nothing wearying about them. They never complained or argued, never took advantage of anything Tod had or did, and in fact became the most helpful and loving companions he had ever known. They were young, but strangely mature for their 25 years. But their maturity did not seep into their play; each and every time they undressed and came to Tod, they were playful and happy and uninhibited. And Tod never tired of them or grew bored because these times of spontaneous sexual activity were frequent and often.