Having been disowned by the Lord and Lady Silther (who went on to quickly adopt a younger cousin of Savin's as their new heir and did their best to avoid discussing the sudden move), and with nowhere else to go, Savin spent the first few weeks after graduating Hogwarts sleeping on the couch at Spinner's End and waiting for his apprenticeship to begin. He had shown up on the doorstep only hours after getting off the Hogwarts Express with Rose (she had decided to ride back with him one last time instead of apparating directly home with Snape), still in his Hogwarts robes and carrying only the single trunk he had brought to school. It was Snape who answered the door, taking in the younger man's red-rimmed eyes and clenched jaw for only a moment before stepping aside and gesturing him into the house, informing Savin quietly but firmly that he would be staying with them until he was able to move into the small apartment off Diagon Alley that would be his to use during his apprenticeship. Rose came down the hidden staircase from where she had been unpacking her things, echoing Snape's invitation and doing her best to steer the conversation away from what Savin clearly didn't want to talk about by teasing Snape for his lack of subtlety in making it very clear that Savin was going to sleep on the sofa in the living room and not anywhere near Rose's bedroom. Snape denied it, claiming that he had just been reminding Savin that the house was too small to have a guest room, so the only place to put him was the couch, but inwardly was a little surprised at how quickly he had fallen into "protective father mode" at the prospect that Rose's fiance would be sleeping under the same roof as her, despite the fact that he himself was barely 11 years older than the pair and wouldn't have expected himself to care either way whether they were sleeping together.
The first few weeks of summer passed quickly, and soon Rose was helping Savin move into his new apartment, a small, cramped place above a shop down one of the back alleys branching off from Diagon Alley (not that there was much to do, as the apartment came fully furnished and Savin didn't have many things to take with him anymore), and making herself at home in the house on Spinner's End (there was no point in getting her own place and having the house sit empty most of the year while Snape was at Hogwarts). They quickly settled into their new routines and new positions - he working as an apprentice artificer for Gringotts, she studying for her potions mastery in a little shop with a master as brilliant as he was eccentric. They met up almost every day, to have lunch together in one of the little cafes scattered through the Wizarding Alleys, or go out for dinner and a movie in the muggle world, or simply sit and talk or work on their various projects in the kitchen at Spinner's End. They had decided to hold off on getting married for a few years, until they were both a little better settled (to Snape's immense relief, he not being quite ready to handle the idea of being "father of the bride" or frankly the idea of Rose and Savin getting married at the age of 18), but were still very much in love and taking advantage of their newfound anonymity in the greater world to publicly go on dates in a way they had never quite managed at Hogwarts.
Time passed quickly, marked out in inventions and research papers, potions brewed and lessons learned. Harry Potter began his time at Hogwarts, setting the wizarding world abuzz, and giving Snape something new to complain about when he came home for holidays or met up with Rose and Savin on his infrequent nights off, to the point where Rose threatened to impose a "No Harry Potter talk at the table" rule. Of course, sometimes the gossip that Snape brought back from Hogwarts was more troubling than how bad Harry Potter was at potions, or how he seemed determined to drive Professor Snape to insanity before graduation. News of powers stirring, dead unicorns in the Hogwarts woods, the Dark Lord possessing another professor, the Chamber of Secrets opening... these pieces of news they stored away, trying not to worry about things completely outside their control, but with a nagging feeling that they would not be able to avoid such things forever. Savin completed a three year apprenticeship, gaining credentials as a master craftsman shortly before the escape of Sirius Black from Azkaban, a piece of news that had been impossible to ignore for Rose and Savin, and not only because it had more chance of affecting those outside Hogwarts as well as those inside it.
Snape had, unsurprisingly, been very concerned about Black being on the loose, and instructed Rose and Savin to be extremely cautious. There was no clear information on where he had gone or exactly what he wanted, but a dangerous madman on the loose would always be cause for concern, and Snape had more than one passing thought that Black would likely be more than pleased to get his hands on the people who his old rival cared about. Not that Snape had any particular reason to think Black would go after him or his family, but when dealing with a man who had tried to get him killed as a teenager, Snape was not willing to take any chances. Savin had already planned on moving to a new apartment when his apprenticeship ended, but Snape convinced him to look outside the Wizarding Alleys, hoping that it might be a safer place, a place less likely for Sirius Black to attack. He ended up finding a place in the muggle world, not too close to the entrance to Diagon Alley, though close enough that he could walk to the shop where he was now working if he really wanted to (though as a practical matter he usually used the floo network to get there directly). Rose remained in the house on Spinner's End, though with plans to move to Savin's new apartment in the near future, now that they had finally set a date for their wedding the following summer. She finished her mastery slightly less than a year after Savin, deciding to continue working with her former master in his shop. By that point Sirius Black had officially been captured and lost again, but with Snape forced to admit that he at least wasn't a Death Eater or mass murderer, the danger and stress levels in the Snape household (such as it was) were back to more usual levels (except of course for the natural stress that arises from trying to plan a wedding, even a simple one).
The wedding of Rose Aurum-Snape (for that was the name that she had begun using after graduating from Hogwarts) and Savin Silther took place on the Hogwarts grounds overlooking the lake, right near the tree where Savin had proposed four years before, the same tree where the two of them had spent many days in all weathers and emotional states. It was fitting, perhaps, that the tree that had seen some of the best and worst moments in their time at Hogwarts, that had watched them grow and change but never lose each other, should also stand witness to their wedding. It was a small and simple affair. Neither Rose nor Savin had any family other than Professor Snape anymore, with Rose's parents dead and her stepbrother estranged (she did send John a letter informing him that she was getting married, but never received a response) and with Savin's parents still refusing to acknowledge his existence (Savin didn't even bother writing to his parents, sure that they wouldn't bother to read it if he did). The ceremony was attended mostly by members of the Hogwarts staff, with a few friends (or more accurately, acquaintances) from either Hogwarts or their time since then, and Professor Dumbledore performed the ceremony. Rose wore a simple white dress with her necklace visible above the neckline, and a wreath of miniature white roses holding on her veil, and she carried a bouquet of white roses and lilies. Snape, looking happier than most of those present had ever seen him, walked her down the aisle to where Savin waited, splendid in dark dress robes and grinning from ear to ear.
The couple had made each other's wedding rings. Rose's was the missing half of her engagement ring, engraved with the wedding date and the couple's initials: RAS for Rose Aurum-Snape and SSA for Savin Silther-Aurum. Savin's was a single piece, a match to Rose's wedding band with the date and initials, with the addition of an engraved cat and fox curled around each other. There had been much discussion between the two of them in the months leading up to the wedding over what their last names should be, and that had been the final conclusion, with Rose keeping the name that she had taken after graduation, and Savin adding her original last name to his parents'. Their future children, they planned, would be Aurum-Snapes as well, since Savin had no interest in his children having any connection to the Silther name. He had considered dropping it from his own name altogether, and taking Rose's entirely, but had eventually decided to keep it. He had been a Silther for 18 years before being disowned, after all, and couldn't quite bring himself to get rid of that last remnant of what had been his family for most of his life. And as Snape pointed out after hearing the same discussion playing out for the umpteenth time in the Spinner's End kitchen, he could always stop using it later if he changed his mind.
It was a magical ceremony, quaint in its simplicity, and there was barely a dry eye to be found by the time they were declared man and wife. Snape claimed he must have just gotten something in his eye, much to the amusement of his daughter and new son-in-law, but he was smiling as much as they were. Cake was eaten, well-wishes delivered, and for a while dancing and laughter filled the Hogwarts grounds. All too soon, however, even that most joyous of days had to come to an end, and the newlyweds set off together to begin the next chapter of their lives. They set up house in the apartment Savin had moved into the year before in muggle London, and continued with their respective jobs. Snape had offered them the house on Spinner's End to live in, but wasn't terribly upset when they hesitantly admitted that they'd rather have a place of their own for now, a place they could make their own. The couple settled into a new routine, not too different from before, but feeling infinitely different because they were doing it together. All seemed well for the Aurum-Snape family, but little did any of them know that this was simply the calm before the storm.