Jack was born to Bert Hsieh and Wendy Lee in the colony of Miridem on August 7, 2540. As a toddler, he grew up with his two older brothers, Henry and Jim, in their home town. The three brothers were orphaned when the Covenant attacked Miridem and killed their parents in the year 2544. They were rescued in time by the Platinum Team, which escorted them to the nearest transport, successfully keeping the three children from enemy fire. The SPARTANs inspired the three brothers to become SPARTANs themselves in order to protect other civilians from the Covenant.
Team Dao was aboard Kano Station during the Battle of Earth. The Spartans defended the station from boarding Covenant infantry. While treating a wounded marine, Seung-ah was shot thrice in the right side of her back by a Covenant carbine. Although she did not flinch from her wounds due to the effects of the 009762-OO drug, Henry ordered Jim to escort her to the ship's cryo facilities, knowing that she had little time. When it was clear that Kano Station would not survive, Henry-G066, Jim-G067, and Jack-G068 escorted surviving crew members to the station’s lifeboats. The Spartans’ lifeboat landed on Mauritania, Africa, and its occupants were stranded. After the end of the war, the UNSC was able to locate and recover the Spartans and the other soldiers.
Attack on New York City
Jack-G068: "Ma'am, take the wheel. I'm going in."
Sam-015: "Good luck, buddy. I know you'll do just fine."
Jack is known for being very observant, making note of and remembering details around him before approaching a situation. By the end of his training, Jack had already accumulated enough information in order to make his own judgements and decisions based upon past experiences, even when presented with information others would find limited in detail. Henry often relies on Jack to give him suggestions on what to do in high-risk missions. Like Dom-094, Jack is an exceedingly careful individual, preferring to keep his distance from his enemies and never taking any risks if he does not have to; this is often contrasted with his older brother, Jim, who can sometimes be reckless beyond reason.
Also like Dom-094, Jack-G068 lacked self-confidence as a trainee, always performing below the levels of his brothers in physical training exercises. Jack often lamented the fact that he was physically inferior to his brothers, not realizing that it was just because they were older and could pick up things more quickly. However, Jack has always had very high expectations of himself when it comes to the more mentally-inclined fields of military, making sure he can execute such tasks to the best of his ability.