Standard disclaimers apply.
It took George a few days to figure out that there would never be an adequate way to say good-bye. There would never be the right words, or the right music, or the right gesture. He wouldn't get that one final joke, one more smile and a wink, one last laugh to make letting go a little easier, because Fred had gone too suddenly for that.
He had never slept alone in a room before now. Mum had wanted him to stay at the Burrow, at least for a little while, but he had insisted on going back to the little flat about the shop. When he had gone in for the first time after Fred had died, he had stepped carefully around the half-unpacked shipping boxes, full of Styrofoam peanuts and new joke products, because Fred had left them that way. The boxes stayed for two days, and then George went back to work and put them away. He never finished unpacking them.
It was thankfully busy in the shop during the day, but he regretted his decision to sleep there at night. The darkness was yawning and empty, and for the first time in nineteen years, there was no one breathing in it with him, the steady sound of it lulling him to sleep.
Time passing didn't take the edge off, either. Coffee didn't take the edge off. Visiting his family didn't take the edge off, and bright, sunny mornings definitely didn't take the edge off. After one bad night and an equally horrible morning after, he discovered that even whiskey didn't take the damned edge off. He supposed he would just have to soldier on through it. Some days were better than others.
With every week that passed, it felt like he was getting further from Fred; further from the period in his life that had had Fred in it. He imagined himself as an old man, looking vainly into the mirror and trying to see Fred's face instead of his own, because it had been seventy years since he'd seen it last and it didn't come so easily to memory anymore. Seventy years. I should be so lucky, he thought dryly.
Sometimes he braced himself against the sink, leaned his forehead against the mirror, and wondered what that seventy y ears was going to be like. He would meet and become acquainted with people who had never known Fred; he might marry someone who had not met his twin; he might have children who wouldn't know more than echoes of the uncle that had passed out of this world a long time before they came into it.
George also knew that he was never going to be able to say, 'I have four brothers', because that wasn't right. Saying that he wasn't a twin wasn't right either. Explaining that to people was going to be rough, though. What would he say? 'I have four live brothers and a dead one'? Was there any way to say it that didn't exempt Fred from the head-count of brothers, but at the same time didn't invite further questions about him?
George didn't want to think about all of these things, but they were all he thought about anyway.
He went to the cemetery once, after the funeral. Standing in front of the headstone shaped like a giant 'F' (Fred would have bust a gut laughing at it, which was mostly why George had bought it), he had wondered how this could be the sum of someone's life. Then he realized that it wasn't, because Fred wasn't there. George remembered him at the Burrow, and at Hogwarts, and at the shop, and those were all the places that Fred was. The headstone was useless. So, he did his grieving from home after that and saved himself the trip.
It would be a long time before he packed up Fred's things, stored what he needed, and gave away what he didn't. He finished the task on the night before his wedding and it somehow made him feel like that made Fred a part of it. It was a revisiting of old times on the eve of something exciting and new. He asked Charlie to be his best man and they poured out a drink for their fallen brother, and then wandered about all night, bottles in hand, singing lewd songs that almost got them arrested. Fred would have been proud.