Rose, Al, and Scorpius had been friends since first year much to the surprise and chagrin of their parents. They enjoyed each other's company though perhaps it was Rose and Scorpius who enjoyed it the most though neither ever had any plans to admit that to anyone, much less each other.
In their second year they learned Rose had a nightmare problem after touching an item in the Room of Requirement, a curse likely. Through her dreams she suddenly knew so much more horrible history of Hogwarts than anyone ever had.
She insisted that Hogwarts was alive and that the Room of Requirement was it heart and she had just happened to touch the part where it kept it darkest memories. They didn't doubt her after she told them about the Founders.
By their fourth year her dream were worse than they had ever been, waking her screaming. It was then that they learned the cure to them, she needed a pillow.
Not just any pillow mind you, she needed a living pillow. A man-pillow to be specific.
Scorpius had been holding her one night as she dried her tears and calmed down and before they had even noticed they had drifted off to sleep. She didn't have any more nightmares that night.
From that night, Scorpius allowed himself to be used as a pillow on most nights, other nights Al took his place.
They learned that when Al was her pillow she could go days without nightmares but they'd have to deal with a terrible mood for those days until the nightmares came back while when Scorpius was her pillow, she had to use him every night as a pillow or her nightmares would come back but she'd be happy when she woke.
As exhausting as it was, Scorpius was all too happy to be her pillow, they created a system, switching beds every night, he'd lay down with a book or notes or whatever it was he wanted to do and play with her hair as he read until she fell asleep before he slept.
By their fifth year, she was quite the cuddler. They both had many things to study for in their exams and Scorpius often found himself sleep deprived while Rose was as chipper as a chipmunk. Which made him happy.
He didn't know why but when she'd wake up in the morning with her arm pinned beneath him (It ALWAYS ended up underneath him and they had no idea how) and she'd smile at him and thank him for being her pillow he was happy.
That was when he knew that he loved her.
In their sixth year, Al decided they should try to wean her off of them, saying they wouldn't always be there for her. So they gave her a man sized pillow and kept guard over her bed in case it didn't work.
It didn't. They kept having to slip under the covers with her to calm her halfway through the night every night.
One night, three weeks later, on Scorpius's watch, Rose refused to look at him as she tried to cuddle with the pillow and failed to get comfortable. She didn't want to trouble her friends.
"You asleep yet Rose?" She froze her forced soft breathing.
"No."
The bed dipped beside her, "Ro, If you can't sleep, just tell me and I'll be your…. Pillow."
Rose smiled slightly at his words before frowning, "But Al's right, I can't always rely on you guys to be here to be my…. Pillows. When we graduate, what then?"
There was a silence for a moment, "Rose I would want nothing more than to always be there for you when we leave Hogwarts and I promise you I will do everything I can to do so. So for now scoot over and make some room for me alright? I'm tired."
She smiled and moved over, making room for Scorpius in her bed. She immediately cuddled up to him as he laid down, chuckling at her.
She rested her head on his chest and could hear his heart beating as she did. It was faster than it had been fourth year when they had started their habit.
Just as they were nearly asleep when Rose asked the question that had been nagging at her mind for the past two years, "Why do you never mind being my pillow Scorp?"
Half asleep he answers without thought, reveling instead at the warmth resting on his chest, "If the most I can be for you is a pillow than a pillow I'll be, It's not like aim gonna make you be my girlfriends when all you want is a pillow."
"You want to be more than a pillow?" Rose looked up at him, hopefully.
Scorpius froze as he realized their conversation at last, "…. Uh…. Yeah? Not- not that that means I want to push you into something you don't want. I'm fine with being a pillow, really…"
Rose laughed, "I don't want you to be my pillow Scorp. Or at least not just one."
Scorpius looked down at her with a hesitant smile, "You wanna try out being more?"
Rose nodded sleepily, snuggling closer to him.
Scorpius grinned, "We'll talk more in the morning then."
That morning they woke to an indignant "Oi! I thought we were trying to get ok with sleeping without us!"
Scorpius opened his eyes sleepily, "Oi Al. Keep it down will you, we're tired. It wasn't working and I swear," he grinned, "If you wake my girlfriend up I will Avada you."
Al's eyes widened as he looked between Scorpius and Rose, "Oh…. Shoot. That's gross dude, she's my cousin!"
In their seventh year, neither Rose nor Scorpius had ever slept so well. She grew anxious as she asked him what they planned to do when they graduated when he finally sighed in amused frustration.
"You know, Rose, I was going to wait to do this until after we graduated but since its worrying you so much..." He got down on one knee in the middle of the Hogwarts Corridor and pulled out a ring, "Rose Weasley will you marry me and allow me to be your pillow for the rest of our lives?"
Rose's eyes filled with tears as she tackled him in a hug and screamed "YES!"
They were married (With their parents' permission) the day of their graduation in the Great Hall.