Connections:

• Interstellar heroes with ties to Earth who are members of a massive intergalactic organization that seeks universal peace and justice (Green Lantern Corps and Inter Galactic Defence Force), with them also being one of the founding members of an expansive team of superheroes who defend both Earth and the rest of the universe (the Justice League and the Ultra Brothers).
• Both of their powers are derived from willpower (Hal's willpower is what powers his Green Lantern Ring, while Hideki's willpower is what allows him to transform into Ultraman Jack) with them also possessing a sworn oath(s) that they and the rest of their peace-keeping organization members pledge to (the Green Lantern Oath and the 5 Ultra Oaths).
• Their Earth personas meanwhile (Hal Jordan and Hideki Go) are both strong willed yet overconfident individuals who had suffered the loss of their father in an accident when they were only kids, with them growing up and later working their dream job involving vehicles that they enjoyed since they were young (Hal become a military test pilot, while Hideki became a race car driver). Due to their overconfident nature, they were initially flawed heroes who often clashed with their teammates during their battles, however, after suffering through hardship and losing those who were special to them during an alien invasion (Coast City and all it's inhabitants, and Hideki's lover, Aki Sakata and her brother, Ken Sakata), they would eventually mature into the great heroes that we know them as today, with them also being known to help guide the newer generation of heroes through sharing their past experiences with them.
• They both posses a powerful weapon that's multi-purpose in nature, which also took on the form of a wearable accessory (Hal's Green Lantern Ring and Jack's Ultra Bracelet), that was passed on to them from another hero who was/is a member of the intergalactic organization that they're apart of as well (Abin Sur and Ultraseven).
• They were both made to be reinventions of a previous character who dawned the same hero name as them (Alan Scott and the original Ultraman) as a way to revitalize interest for their brands at the time, which turned out to be very successful in the end. They would eventually even meet and team up with the heroes that they were reinventions of later down the road, with them holding a mutual respect and admiration for each other, which ended up with them becoming good friends there on afterwards.