Willie Lincoln
Willie is Abraham Lincoln's son. Misdiagnosed with a cold when he actually had typhoid fever, the 11-year-old died. Now he awakens in the Bardo, a sort of in-between place before the afterlife, but Willie doesn't know he's dead. He makes friends and witnesses his father at the cemetery with his own -- dead -- body. Trying to latch onto his father in the hopes of surviving somehow, but by the time they do reunite Willie is standing in the Bardo with his dead father beside him.
Abraham Lincoln
Lincoln is a devoted father who never expected Willie's death. He grieves and struggles for sometime with intense guilt because he didn't observe the severity of his son's illness. Finally, after laying Willie's body to rest, Lincoln notices a sort of mysterious pull on him, a presence in his mind where there should be absence, as if Willie is communicating.
Hans Vollman
He befriends Willie in the Bardo. He's an older man who is eager to school the newcomer in the strange goings-on of this liminal space. Eventually he helps Willie reach his father.
Roger Bevins III
Bevins is another new friend to Willie. He's lived an interesting life, which he's loathe to leave behind and enter the afterlife, so he remains a specter.