Charlie O'Neill

Charlie O'Neill was the only son of Jack and Sara O'Neill. He died, shortly before the first mission to Abydos, when he accidentally shot himself with his father's personal gun. Judging from his appearance, he was about eight years old at time of his death.

Jack O'Neill blamed himself for what had happened to his son and came close to committing suicide. However, his adventure on Abydos with Dr. Daniel Jackson brought him out of his depression and caused him to lighten up a little. Nevertheless, Sara divorced her husband shortly after his return from the first Stargate mission.

About a year later, an alien entity, impersonating O'Neill, tried to find Charlie so he could make him "better," but didn't realize how permanent physical death was to Humans. However, the being did impersonate Charlie as Jack took him back to his planet.

Two years later, when torturing O'Neill for information on Ne'tu, Apophis used the memory of Charlie's death.

It is possible that Charlie would have the ATA-gene like his father.

Alternate realities

 * In an alternate timeline created by Ba'al, in which the Stargate Programme never happened, an alternate Jack O'Neill has said that Charlie is still alive and still lives at home with him.
 * In another alternate timeline Charlie has a half-sister who is the daughter of Jack O'Neill and Samantha Carter.

Behind the scenes
In the film, the character's name, as it appeared on a certificate, was Tyler O'Neil. It's been speculated that "Tyler" may be his actual given name and that "Charlie" is only a nickname. In Bill McCay's Stargate novels, the character was named Jack O'Neil, Jr. after his father.