SO I found a post and it said something along the lines of this: Imagine George Weasley sending his son to Hogwarts for the first time, and his son is sorted into Gryffindor and everyone is very happy. But one day at school he calls home, highly distressed, asking if his father is alright. George keeps reassuring him "yes yes im fine im fine nothing happened, what's wrong?" and his son says, "There's a ghost here who looks exactly like you."
and so my addition is this...
After recieveing the phone call, George immediately grabbed a Quidditch broom and apparated as close as he could to Hogwarts. He then hopped on the broom and flew the rest of the way. He didn't care that he looked insane. He did not care that he could be arrested. He soon made it to the school itself and landed, bounding inside before anyone could react. He ran through the halls as the teachers were notified that a strange man was in the school. He didn't stop. Not once did he stop running. That is, until he saw him. George stopped, and he stared. For, floating in front of him was Fred Weasley, his twin. Fred opened his mouth and said, "Hello, George." And that's when the tears fell.
After George had been caught by and questioned by the teachers, they decided it would be alright if he visited the school. But he didn't want to just visit the school. He wanted his brother back. He explained this to them, more than once, and those who had known the troublesome boys in their youth felt such pity that they just felt they had to try. So with many pulled strings and one ghost finally retiring, they offered Fred and George a job. If they wished, they could co-teach Magical History. However, they would not tolerate them destroying everything. The twins agreed instantly. George, of course, could not give up his shop, so instead he hired some people and ran it from afar during the school year, when teachers were needed. He told Fred of the success it had become, and of his wife, and their children. Fred, in turn, told him of all the students he had befriended. And in class, well, history was no longer boring. It was filled with exciting activities and games, a few lectures here and there. They never had a single student fail their classes. And they had never been happier.
Many years later, George grew elderly, and very sickly, and he had to resign. He lived in a hospital now. His children had long taken over his business, the one he stared with Fred. He hadn't seen Fred in two years. He missed him, very much. It was as though Fred had died again, and he hadn't become a ghost. Except, now it was George who was dying.
George managed to sneak out of the hospital at one point. It was difficult, but he did it. And he apparated to Hogwarts again, broom in hand. And he flew into the school, which was empty and quiet, because it was summer. He used his secret passages to get inside the school. He walked up the magical stairs slowly, and they stilled for him, as if sensing his pain. The paintings watched him curiously- worriedly. A few went to go and get him some help, sure that he was not supposed to be there, yet stopped when he begged them to. But still George climbed, and he didn't stop climbing until he had reached the Clock Tower. He saw Fred gazing out at the landscape, and knew that he must have been remembering all the times in his middle age when they would sit there and grade papers and discuss their students and the news. And the sunsets.
He sat next to Fred's ghost, and neither said a word. They just sat and stared at the beautiful scenery, until the sun set and the stars came out. "Hello, George," Fred said, a grim smile on his face. George laughed a little, told him to lighten up. And then George began to talk about how his grandchildren were growing up beautifully, with the famous Weasley red hair and freckles. And then Fred joined in, talking about his students from the past two years without George, and how they had grown, and the adventures he helped them to have, wandering the halls at night, sneaking into Hogsmeade. They talked until morning, and George fell asleep.
It took Fred a long time to realize his brother wasn't breathing. And when he did, he was flying faster than he had ever flown on a broom, calling for help. The teachers who stayed year round came rushing to his call, following him up to the clock tower. They said the words five times before Fred realized, with horror, what they were saying. "George Weasley is dead."
Fred mourned. He mourned the lost time with his twin, but he also mourned the time he spent with him. George was his life. He was George's life. Nobody could approach Fred for weeks, as he would simply run away or begin screaming as though in agony. George Weasley is dead. Well, so was Fred. So where was George? Where was his brother? It wasn't fair! Why couldn't he find him?! What happened?! George Weasley is dead. So why isn't he a ghost?!
When school started again, the teachers had to find a substitute for Fred. They were still hopeful that the normally happy and mischievous ghost would return to normal. They were hoping they wouldn't have to force him to move on to keep him from becoming vengeful. Students tried their hardest to get the ghost to smile, to make him happy, but he only seemed to get worse. Eventually, winter rolled around, and the teachers decided it was time.
On the day that Fred would be sent to the afterlife, something strange happened. The paintings were all calling for the Weasley ghost, trying to find him, shouting at him to go upstairs, go upstairs! He needed to go upstairs! He needed to go now! And so the moping ghost did so, slowly, ignoring the urgency in their voices. "Go to the clock tower!" The Fat Lady cried as he passed. The clock tower? Fred moved a bit faster, suddenly the cries sounded like encouragement to get a move on. He flew faster and faster, until he reached his destination, until…
"Hello, Fred." And that's when the tears fell.
That was the day that the Twins of Gryffindor came to be.
basically after they came back together, the two became the history teachers again, and became somewhat of a symbol for Gryffindor House. They became known as the Twins of Gryffindor, a carefree pair that actively try to get the students to cause mischief and definitely help them sneak around. They always watch over the Weasley family line as well, as they tend to be much more trouble than they're worth…