Sexy Succubi and Siblings - part 3

Part 3 is shorter, but pretty full on. I hope you like it. Does anyone want part 4 etc?

Inside Susan's mouth, her tongue licked at Robert's shaft.
" Do you think that is all? ", the Succubi questioned with glee. "We are creatures of magic and we are in complete control!"
Robert felt his cock lengthen and go even further into his sister's throat. It was unbelievable. I felt amazing, but he looked into Susan's eyes where tears cascaded down her cheeks. "Are you okay?" Susan nodded as much as she was able. Then she started humming. Her lips vibrated his shaft gloriously.
Incredibly his dick lengthened more. It was hard and yet flexible at the same time. It had a life of it's own as it passed through her esophagus and down into her stomach!
"But we are neglecting Susan's desire. Her nipples grew and grew. So very long. They were so long that she felt one open her wet pussy lips and the other one felt like a tiny a small mouth fastening onto her clit.
MMMMmmmm moaned Susan which increased Robert's pleasure.
His cock entered Susan's small intestine. He was lost in lust. But he needed to Cummnrmm.
" Oh no " the Succubi told him you will cum only when we want you to "
Longer and presumabtly thinner, it probed it's way into Susan's large intestine. Robert had some knowledge of the human body and he wondered if he would push into something nasty, but it was clear and tight! Robert felt like he had released as much pre-cum as much as a normal orgasm. Further and further into her rectu
Susan moaned and groaned, as much from Robert's incredible probing and also from her manipulated clit and pussy.
Robert had reached a really tight spot.
"Well done my young slave. You are about to be the first ever to push through a sphincter from the other side."
His cock swelled and then went thin, probed for the opening!
"Aarrgh" came from Susan's throat as Robert's dick burst through her anus and felt the cooler air.
"Now for a reward" the Succubi chorused. Robert felt that feeling that there is no stopping and great squirts of cum flew from the his dick and half way across the room.
Susan's manipulated nipples pulled and sucked harder and faster and she blacked out for a few seconds as a tsunami of orgasms waved through her body.