Nicholas Ballard was the archaeologist grandfather of Daniel Jackson. However, since childhood, Daniel addressed him as "Nick." When Daniel's parents died, Nick was too busy with his travels to bring him in.
In 1971, Nick discovered a mysterious crystal skull in Beliz and was transported to another planet, where he met giant aliens made out of mist. However, when no one, not even Daniel, beileved his story, Nick had himself committed to a psychiatric institute in Oregon.
In 2000, SG-1 brought Nick to Cheyenne Mountain to solve the mystery of Daniel's disappearance. Nick ended up returning to the planet he had visited twenty-nine years ago by Stargate. Nick choose to remain on the planet to teach and learn from the alien beings. (SG1: "Crystal Skull")
Behind the Scenes
In the episode "The Other Side," Daniel stated that his grandfather was Dutch. However, it's not clear whether he was referring to Nick or his other grandfather.