He does not know how it began, the light kisses in the hallways or the heated fumbles in the empty classrooms. He does not give much thought to it, despite knowing that his father would balk and his mother would throw a fit - "The Martells!", she would say, she disapproved, always disapproved . In a sense he is like Sansa, looking for romance in all the wrong places, and Arya, throwing caution to the wind and acting on her own whims. But Sansa is in Ravenclaw now, and she's smart and sweet and sensible, and Arya was sorted into Gryffindor like him, where she's learning to think with her head, too, which is why he can't believe what he's doing sometimes. All he knows is that he is Robb and she is Arianne and they are both beautiful and powerful.
But he loves her, or so he thinks, loves the way his fingers tangle in her hair and loves the way she looks up at him, loves the way the darkness highlights the shadows under her eyes. She loves to admonish him, calls him silly boy, silly Stark boy , and he laughs at her because there is much you do not know, even if you are a seventh-year, Arianne Martell .
She smiles, and her eyes turn to jewels. She is a viper, from the Martell family, and her blood is as pure as they come. Your blood is pure as well , she says, and they are on equal footing again. She is as much her uncle's daughter as he is his father's son, and her laughter is as free as the wind as she twirls circles around him.
It is a dance, what they have, because she is as quick and as lithe as the snake that graces her house and her family's embellishments, and he is as fierce as the wolf and the griffin that graces his, and they chase each other down corridors when no one is looking and he grins, and his teeth are sharp. She kisses him, deeply, and he responds in kind, and for a few moments there is nobody else.
I will be gone soon, she tells him, for she is a seventh-year and heir to her family's business, the world is at her feet.
It is no matter, he says, with that cockiness fifth-years have about themselves. We have all the time in the world.
They do not.
It is Quentyn who finds out, Arianne's sweet brother who'd gone the way of Aunt Elia and gotten himself sorted into Hufflepuff, spotting them during one of their trysts. They do not think much of it, for Quentyn is young and easily coerced, but they are not much older themselves, and thus they are unaware of the consequences of beauty and temptation, and Quentyn winds up telling Sansa (who is like Robb, so like Robb), and eventually Ned Stark himself comes booming down upon them.
You defile the Martell girl! he says, and Robb says nothing, he did not do the defiling. Have you no honor?
She is a pureblood, Robb replies. You did not like Jeyne; mudbloods had no place in this family, you said. The Martells are as pure as they come -
But they are the Martells, Robb, do you not see? his mother yells, and his face sours. Uncouth and uncultured as they are -
That is absolutely ridiculous, says Robb, but his parents only glare at him and his siblings stare at their food.
He tells Arianne about it, later, what his family said, and her dark eyes turn to stone. If that is the way they would have it, she says, then it is obvious what the next logical course of action is.
She kisses him last; it is deep and long and her eyes are sad. Good luck in life, Robb Stark, she says on her last day. We will meet again.
Robb says nothing, he just nods and agrees with her. He has his own kind of honor, he likes to think.