Headcanon that Albus and Scorpius share a compartment in the Hogwarts Express and make the pact to be friends no matter what. They don’t mention it, but that pact is very important to them. Scorpius would be the first friend Albus makes that is not family. Albus would be the first friend Scorpius makes, period.
When, against all odds, Scorpius is sorted into Ravenclaw, Albus has to fight back his tears, because he knows, he knows, that he is a Slytherin to the core.
But, sharing a candy feast during your first trip to Hogwarts must be the cement of a true friendship, because Albus and Scorpius do become the best of friends.
They start sharing meals together during their first week, and never stop. They don’t make friends with their housemates, and people look strangely at them, but they don’t care. They have each other.
Scorpius is the only one allowed to call Albus by his full name, because he likes the sound of his name on his friend’s tongue. Albus is the only one who has ever called Scorpius Scor. It makes him feel special.
Albus has never sat in an armchair in the Slytherin common room. Scorpius barely knows the color of the walls in the Ravenclaw common room. Because every free time they have is spent together, working in the library until curfew or lazing around by the lake.
Once, Albus gets caught returning to the dormitories slightly after curfew, because that night, Scorpius didn’t say him goodnight, he hugged him goodnight, and he was so confused that he got lost on his way back. He gets detention by his head of house, the potion master.
The day after, Scorpius spills the content of his cauldron on the floor on purpose to get detention with Albus.
It was in 4th year. It took Albus a whole year to understand what his confusion meant, and by then, Scorpius doesn’t only hug him goodnight, he’s also started to kiss him goodnight. On the cheek, but still. It doesn’t fail being the best part of his day.
Once Albus has put a proper name on his confusion, it takes him a week to tell his best friend. Courage has never been his strength, but there is nothing, nothing, he doesn’t tell Scorpius. So one thursday night, he tells him.
And Scorpius tells him back.
There is no surprise in their parents’ eyes when they announce their love.
The first time Scorpius makes love to Albus, Scorpius cries. He’s never been happier and can’t help but think he doesn’t deserve someone as generous and beautiful as his boyfriend. They don’t leave the room of requirement that night.
Neither did they the nights after.
Once they graduate, they take a flat together. Sorpius’ parents give them the Malfoy crockery and Albus’ parents give them the Black silverware. No one gives them proper furniture, so they spend a whole day in a Muggle shop trying beds and opening kitchen drawers.
They got married a day of January. When Scorpius tells his vows, his mother cries. When Albus tells his vows, Scorpius cries.
They adopt two babies. They call them Altair -from the Eagle constellation- and Alya -from the Snake constellation.