I have not been able to stop thinking about Jegulus and Pandalily co-parenting Harry and Luna.
Regulus and Pandora knew they were gay but were forced into an arranged marriage by their parents and ran away either a little before or a little after Luna was born.
Jilly are highschool sweethearts who got married right out of school, only to realise after Harry is born that they love each other but aren't in love with each other (if that makes sense).
Both couples break up but stay best friends of course.
Then Pandalily and Jegulus get together.
Luna and Harry grow up as siblings with two mums and two dads.
James is 'Dad', Lily is 'Mum', Regulus is 'Papa' and Pandora is 'Mama'.
They all live in a house together as a family. Happy ending.
(bonus: Sirius and Remus raising Teddy alongside them. One big happy family)