Charlie-Cecilia
Alec is a Muggleborn, Alec's parents hate that he has magic and tried to beat it out of him. They continue to abuse him for years, Alec's only escape is Hogwarts. But even there he has to deal with cruel pure bloods who despise him for being Muggleborn. One night the abuse is so bad that Alec's parents almost kill him, but Harry saves Alec. Harry wants to send Maryse and Robert to Azkaban but because they never abused Izzy or Max no one will believe him apart from Draco who was the only other person to see Harry save Alec.
Harry and Draco adopt Alec as his parents don't want him and Alec is afraid to live with them. Harry wants to adopt Alec's siblings too, but Maryse and Robert won't let them and Alec's siblings don't have magic. Being adopted by Harry Potter makes Alec famous but he hates the fame. Alec was always more comfortable in the shadows not the limelight. But he is shown parental love for the first time in his life which makes it worth dealing with the struggles of fame.
Alec has had a crush on Magnus for years but has been too afraid to say as Magnus is from a pure blood family. But Magnus surprises him by asking him out, Alec is wary at first but begins to fall for Magnus.