"Now I’m the saintlike one, George," Fred murmured from behind his sobbing twin. "You’re holey, but I’m dead."
But of course, George couldn’t hear him. Too focused was he on the corpse, and Fred wasn’t a ghost, not yet. Still, he had to choose between haunting forevermore, or going into the afterlife - whatever that may be - and meeting his heroes, the Marauders. Between staying there for his brother, spending eternity helping kids pull off pranks, or going and waiting for George in the afterlife. After all, in decades, when George would die, he likely wouldn’t want to be a ghost for eternity - especially seeing as he wouldn’t die at Hogwarts, and thus they’d be separated for eternity after. And Fred knew his Georgie - if he stayed, George would spend day after day at the castle, talking to him. He wouldn’t be able to let him go. Thus it was with a heavy heart, so unusual for the lighthearted prankster, that Fred kissed the top of his other half’s head, muttered, “Keep the joke shop going, Georgie, I love you,” and vanished entirely.
When Fred dies, George gets rid of any and all mirrors and highly reflective surfaces. He refuses to look into them when he's near, so much so that his parents cover them when he visits. After he marries Angelina, and they move in together, he still refuses to allow mirrors in his house. Just the same once his children are born. Still, through all of this, he has had a ritual. Once a year, on April First, he goes into a small, typically locked room, and turns the light on. Inside is only a chair and a mirror. There he sits, facing the mirror, and sings happy birthday to himself and his reflection, birthday cake in hand. "Happy birthday, Fred. I'm another year older, you're another year colder." He eats the cake and sets the plate on the ground, then proceeds to fill Fred in on what he'd missed in the previous year. After he has, he picks up the plate, turns off the light, and leaves, locking the door behind him. He doesn't speak about this to his family, they do not attempt to speak about it to him. They have no mirrors in their house.