A hopeless romantic, Sansa was doomed to be the first of her siblings to catch on to her eldest brother's escapades. It's not that she hadn't suspected it before (she wasn't stupid, Arya) but of Eddard Stark's other five children, having Robb beat her to romance hurt the worst. Willful ignorance of the situation was only to be expected. As long as she just gritted her teeth and closed her ears to the extremely suspect noises coming from Robb's chambers at night she had no reason to be disappointed.
Closing her ears didn't help so much, though, when the evidence was laid out clearly for all to see through a nudged-open chamber door. Sansa wasn't spying. She wasn't! It's just that, for one thing, those noises only ever came from Robb's room, not Theon's, and the choked-off moan emitted from the door's gap sounded almost painful. It was only logical to peek in and make sure that nothing bad was happening, of course.
It had been a lovely morning and even lovelier noon, with the sun shining bright and dappling the ground where it shone through the leaves of the weirwood. It was only a couple of hours since Sansa had returned from the said tree, too enraptured was she by its beauty that summer day, but the light that streamed through the window of Theon's chambers illuminated everything inside to a dazzling degree.
Never had Sansa hated it more.
The sun was dappled here, too, although instead of setting the red leaves of the forest floor aglow, it brought out the red flush on her brother's cheeks to a startling degree, nearly masking his freckles and bringing his skin to an uncannily similar shade with his hair. Hair that was far more unkempt and sweat-damp than it had been only an hour ago when Robb had left luncheon with...
Blue eyes bulged as two and two were connected; the overeagerness with which Robb had left the hall, the sly glances that Theon thought went unnoticed between them, the damned whispering and the knowing and often exasperated looks Jon had shot at them both… and now whatever in the Seven Hells she was seeing before her.
I've been a fool! Sansa silently bemoaned. A hopeless, ignorant fool!
The blush didn't stop on Robb's face, though. Sansa was quick and alarmed to discover that both Robb and Theon, propped up on the bed frame and upon whose lap the former was stradling, were entirely topless. A pale hand ran down her brother's equally freckled back, coming to rest at his hips as they ground against his partner's. The other hand grasped a (thankfully) still-clothed thigh. Both of Robb's hands were preoccupied, as well, tangling together in dark hair, pulling the two face-to-face in a heated, noisy kiss.
Seven Hells, thought Sansa, petrified in the doorway. Seven bloody Hells. I shouldn't be here, I shouldn't be here! But try as she might, her eyes wouldn't avert from this poorly hidden secret moment between her brother and her father's hostage. Come off it, Sansa, just leave already!
Her internal debate was interrupted by a particularly lusty moan from Robb, who had thrown his head back as Theon's attention moved to his (just as freckled) neck. The hand that had been on his thigh had at some point moved to where Sansa could not see but assumed to be the ties on his breeches if the movement of his arm was anything to go by. The one on his hip had also dipped down further into the back of the breeches, rousing a visible shudder and a low groan from Robb. Now, Sansa was a girl of thirteen and although she had never done anything like that before she had heard the bawdy banter in the court and had learned enough about… human physiology … from her Septa to know what was likely happening where her eyes could not glance. To see it happen though (and to her straight-laced, honorable older brother, no less)...
Her brother's hands had drifted downward, as well, gracing over an unblemished ivory collar, past the archer's defined chest and coming to rest lightly on his abdomen. This elicited a flinch and a breath of a laugh from Theon, who whispered something that vaguely sounded like " that tickles" before craning his face back up to meet the other's lips once more. This kiss soon devolved into bites and moans, and soon enough Robb was sitting up in Theon's lap with the latter hastily moving to pull the breeches down.
Sansa could watch no more. She had a vague idea of where this was going and had no intention of seeing it firsthand, and especially not to her eldest brother. The pleasured cries coming from that god-forsaken chamber only seemed to grow louder the further she fled.
What should I do?, She puzzled. Going on as if nothing drastically important had happened, pretending she didn't see Robb in a new light and not struggling to look Theon in the eyes after this, that was simply out of the question. Surely what she had just seen was something to bring up with her parents, right? After all, Mother had warned them all (even Jon) never to get close with the young Greyjoy, and close wouldn't even begin to describe what Robb was to him. But bringing it up with Mother or Father would mean indefinite punishment for Robb and Theon, and Sansa would feel dreadful if they were to blame her for tattling.
No, then. Better to bottle this away and bring it up later when she had some time to process it. After all, it didn't seem like either of them disliked what was happening, and something that made Robb happy couldn't be so treasonous as to warrant chastisement, right?
Sansa smiled, just a little.
A noble lord falling in love with an enemy captive, she mused. It's quite like one of those romantic songs, actually.