Twilight had been eager to visit Shining Armor and Cadence for Cadence's birthday. She'd already gotten her sister in law a gift-she'd gotten it months ago when she found a specific crystal empire design that she knew she'd love-and was happy to see that she'd chosen well. Cadence seemed to love it, but it seemed there was more to their visit than they were letting on.
They had asked Twilight if she could spend the night in the castle and leave in the morning. She wasn't sure why, but supposed there was no problem with it, and agreed. She only connected the dots when Cadence and Shining Armor led Twilight to their bedroom, and explained that Cadence had asked Shining Armor for something special for her birthday; she wanted to have both of them in bed with her that night.
It was a rather surprising desire, at least coming from her, but the thought of it had Twilight visibly excited, and saying no when they could both see the tent she was pitching seemed disingenuous. When Cadence walked into the bedroom, she found Twilight and Shining Armor sitting side by side on the bed, both naked with their members hard as stone for her. It was extremely awkward, but they could get through it for Cadence.
Cadence smiled, getting down in front of them and gripping both Shining Armor and Twilight's members in her soft hands. The siblings moaned as they felt her hands move carefully along their lengths, stroking them both skillfully. It was hard for Twilight's mind to properly register how good at pleasing her rod Cadence was, but she supposed there was nothing wrong with her having such a skill. In-princess like perhaps, but as if she were one to call others out for behavior like that at this point.
As Cadence stroked them, she lowered her head, licking along Shining Armor's cock, then moving to mimic the motion on Twilight's. Both kept moaning as they felt this, their cocks growing harder from the stimulation that never lasted long enough for either of them to cum too early. Soon Cadence went from just licking to taking a few inches inside and sucking before alternating.
She stopped when both of them were to the point of leaking pre-cum, getting up onto the bed on her fours and beckoning the two over to her. Shining Armor got in front of her, his member at her lips, and Twilight got behind her, her cock brushing against her pussy. Cadence opened her mouth and took Shining Armor's rod into her throat, Twilight watching in awe for a moment before pushing forward to penetrate Cadence's pussy.
Both moaned as they spit-roasted the princess of love, thrusting into from either side. Both of them were close already from Cadence's handy work before, but held back, not wanting to cum before she did. Cadence got close quickly from the fulfilling of her kinky little fantasy, and came just a minute or so before Twilight did. Twilight had meant to pull out, or at least told herself that she did, but staying inside and creaming Cadence had been too irresistible, and the thought had pushed her over the edge.
Another minute or so later Shining Armor reached his own limit and came as well. Cadence moaned as she swallowed down his hot seed. Twilight moved back as Shining Armor thrust into his wife from behind, as they were meant to switch positions now. Rather than go over to take Cadence's mouth, she lingered behind Shining Armor, her eyes unable to look away from his soft, firm looking ass as it moved, almost bouncing as he thrust into Cadence.
Twilight tried to stop herself, or at least would later claim that she had. This was supposed to just be about Cadence's fantasy, nothing else, but Twilight was too caught up in the heat of the moment. Shining Armor yelped as he felt Twilight's cock ram into him, taking his anal virginity without so much as a warning. Cadence realized what had happened and moaned, pushing her hips back harder as she enjoyed the taboo of the moment.
Shining was frozen for several moments by the shock of what was happening, but the force of Twilight's thrusts into him kept his cock moving in and out of Cadence, who's moans only grew louder as they went. Soon Shining Armor was able to say 'fuck it' and begin moving his hips again, taking Twilight's member deeper into his ass as his own was pushed deeper into Cadence's pussy.
Shining Armor came first a few minutes later due to the over stimulus, clenching tight as a vice around Twilight's cock as she shot warm seed into Cadence. The tightness brought Twilight over the edge next, causing her to unload into his ass. Shining was seeing spots as he felt the seed flood his anus, and his cock let out a few more spurts into Cadence, who reached her climax not long after.
By the time Shining Armor's senses returned to normal, his wife and sister had chanced the positioning on him. Twilight was in a sitting position with Cadence riding her rod. She seemed to be waiting for Shining Armor, and he realized what she wanted. He got above her, thrusting down into her throat. She moaned around his cock, sucking hard as he fucked her throat roughly, getting as deep as he could inside; he saw no point in holding anything back now that they'd left the point of no return in the dust.
Cadence rode Twilight harder as she watched this, Shining Armor's balls hitting Twilight's chin as he want. Cadence grinned mischievously, leaning forward and lowering her head to lick at them, bringing her husband even more pleasure. He groaned as he felt her do this, staying stiff with his cock lodged inside for a few more seconds, close already. A few moments of the double oral attention later and Shining Armor was unloading thick ropes of cum down Twilight's throat.
Twilight managed to hold them all down, though just barely. Shining Armor sat back to catch his breath and recover as Twilight picked up the pace with Cadence, thrusting harder up into her and showing no signs of slowing until they'd both cum. As they panted, Shining Armor picked Twilight up, dropping her into his lap. She moaned as his member pushed into her warm, wet pussy, and Cadence grinned as well, getting in front of them and taking Twilight's member between her large, luscious breasts.
Cadence licked at Twilight's tip as she stroked her with her tits, and began moaning as well when she felt the magic the brother and sister were using. Not wanting to leave Cadence out, Shining Armor and Twilight were both using their magic to play with her pussy, rubbing against and inside of it, and squeezing and rubbing against her clit. All three continued to moan as they go. Things had spiraled out of hand, but none of them wanted it to stop.