He was a born mechanic and enjoyed helping Chubbo take apart devices and put them back together. He grew up with Chubbo, a Chadra-Fan who was a prodigy with tech. They got into all sorts of trouble together, largely at the behest of Chubbo, as Jorn would grumble about the dangers and risks involved, but go along anyway to make sure Chubbo didn't get himself electrocuted or something.
When Jorn was still quite young, the Clone Wars broke out and his home planet became a battle ground. His parents and Chubbo's mother were killed in the initial assault, so Chubbo's father took them off-planet aboard a refugee ship bound for the refugee relocation center on Abregado-rae.
While en route, the ship was raided by slavers who took Jorn and Chubbo along with many other refugees to their base in the Belgaroth asteroid field. Once they were put in the cell and the pirates had left, Chubbo unlocked the cell door and left. He urged Jorn to come along with him, but Jorn refused, saying that it was too dangerous. Chubbo decided to go anyway.
While Jorn huddled in the cell, a couple Mandalorians who had been hired to rescue Chubbo and Jorn found him. He told them where Chubbo had gone, and they sent him over to their ship where they were sending the other rescuees. When they found Chubbo, he didn't believe them and they had to get Jorn on the comm to convince him.
He was reunited with Chubbo's father on Abregado-rae, and a short time later began an apprenticeship with a mechanic on Vorpa'ya at the recommendation of one of his rescuers.
Once he had completed his apprenticeship and came of age, he and Chubbo struck out on their own, starting a business on Lok. After a couple years, there was a violent uprising started by a young Mandalorian and a couple of his friends that drove the Imperials off of Lok. Chubbo and Jorn decided to join the Rebel Alliance, where they would make use of their tinkering skills to aid an independent commando group. Jorn became the group's medic, using his worrying skills to keep them all alive.
Relationship: Childhood Friend
He grew up with Chubbo, and they went through a lot together. He is determined to protect his friend, from himself if necessary.
He is determined to always be there for his friends, even when they are doing stupid things. No matter what, he'll be there through thick and thin.
Personnel: They can't fight the Empire if they're all dead. He is determined to keep them alive in spite of themselves. None of them will ever actually consider the risks, so it leaves it up to him to keep them appraised of the dangers and treat their injuries when they inevitably ignore his recommendations.