You could do a post-war Harry Potter story where the protagonist is Fred's best friend (no one knows her only her name from when Fred talked to his family about her) and one night, days before the battle, they will go to the bed and she got pregnant but they were both happy, knowing that he died in battle, she has her baby alone (she would have a lot of money and would be born muggle) when the baby is one year old she decides that Fred's family deserves to know the only thing what's left of fred Then she and the baby go to visit the madrigera (the baby would be 1 year old and she 18)
The story would be with George (Fred had always fantasized about his best friend and brother dating)