Colin Creevey's brother never visits his grave. Dennis tries to go. He really does. He knows it would make his father so very happy if he went. But he can't.
He knows if he goes he will never leave. If he sees that grave, a part of him will die, and he will leave that part of himself with Colin. He cannot allow that to happen.
His parents don't understand. They are angry with him. But he does it for them, because a part of them had died, and because he knows it wouldn't be fair for them to lose two sons to the war.
After the war, Dennis Creevey goes on.
Dennis Creevey goes on to become a famous photographer for the Daily Prophet.
Dennis Creevey goes on to marry Emma Dobbs, a muggleborn who survived Azkaban. She is the strongest person he knows. With her at his side, he can never fail.
Dennis and Emma Creevey go on to have nine children. Harry, Ronald, Ginerva, Luna, Neville, Hermione, Dennis Jr., Oliver, and George. No Colin. They name their children after the living, not after the dead.
After the war, Dennis Creevey goes on to live a full and happy life.
After the war, Colin Creevey stays in his grave and his memory does not haunt the living.
Which is how it's supposed to be.