Where Have You Gone, Charming Billy?

What do Paul Berlin's memories and fantasies reveal about his family?

They were hostile and argumentative toward one another.
They were indifferent---they didn't really care one way or another about each other.
They were close and loving.

Why can't Berlin stop laughing at the thought of Charming Billy dying?

He really didn't like Billy much.
It was ironic that Billy would die of a heart attack in a war.
He found death more humorous than tragic.