Chapter Text
Everyone knew that the name or names on your wrist belonged to your soulmate. If you were the younger, the name appeared when you were born, while the elder had to wait up to five years to gain their name when their soulmate was finally born. It was also well known that magical twins shared a soul, and thus a soulmate.
As soon as James Potter saw the names Fred and George Weasley on his newborn's wrist, he was on the floo to Arthur, who was about to call him for the same reason. Both couples rejoiced at the future union of their families, and arranged play dates between the trio once Harry was old enough.
When Albus told the two couples the prophecy, the Potters and the Longbottoms immediately gathered Sirius and Remus and Arthur and Molly together to plan. Despite the old man's caution to tell no one, James couldn't imagine leaving his brother out of the loop, and where Sirius went his soulmate followed. Arthur and Molly's inclusion was obvious to him as well, because anything that affected Harry would also affect the twins. Frank and Alice had been a little hesitant at first, but when the others swore vows of secrecy to protect the contents of the prophecy, they were swayed and happily accepted the help.
Together they hatched the plan that the Longbottoms would hide behind the wards of Longbottom Hall with Frank's mother as their secret keeper, while the Potters would hide under the fidelius charm in Godric's Hollow, using Peter Pettigrew as their secret keeper and Sirius Black as their decoy. If anything went wrong, Molly and Arthur were their backup plan, and they would be able to take Harry in and raise him alongside his soulmates if Sirius and Remus were unable to take in their pup. They too would be given the secret by Peter, so that they could bring the twins to visit little Harry. None of them wanted to split up the young soulmates for too long.
The plan failed, of course, because none of them suspected the duplicity of Pettigrew. When Sirius Black was thrown in jail for the crime, Molly and Arthur immediately went to his superior, Barty Crouch, and protested his innocence. Crouch ignored them, and it wasn't until his son was found to be a Death Eater and he lost his position that they could get anyone to listen to them.
Crouch Jr was captured by Arthur Weasley himself, as he and Remus were meeting with the Longbottoms, trying to figure out what to do about Sirius and Harry, when the Lestranges attacked. All four Death Eaters were put down hard, and only Frank suffered any lasting damage — getting occasional shakes from being held under the cruciatus curse by Bellatrix Lestrange.
With Crouch Jr in Azkaban and Crouch Sr a disgrace, the new head of the DMLE, Madam Bones, was far more skeptical of Sirius's guilt, and was willing to investigate what Crouch had ignored. With their testimony under veritaserum that Peter Pettigrew had verbally told them both the secret, the Weasleys were able to get the ball rolling, and six months after his incarceration, Sirius Black was freed.
It was too late, however, as Albus Dumbledore had already whisked Harry off, ignoring the Potters' wills, and hidden him where none of his proposed guardians could find him. Throughout the years, as Albus tried to make the 'Boy-Who-Lived' a household name, the three families shut him down. It wasn't much, but it was what little they could do to honor Lily and James, who had died for their son, and to protect Harry until he was old enough to do it himself.
After years of hammering at Dumbledore in the Wizengamot and getting nowhere, they were out of legal remedies. They assumed Harry was under some sort of Fidelius charm, and that they would not be able to locate him through magical means. Despondent, they were resigned to waiting until Harry was old enough to go to Hogwarts to finally reconnect. They had no idea that fate had other plans for them.