Jude was born in Leronde. He is the son of Ellen and Derek Mathis, two doctors in Leronde. While his mother is Rieze Maxian, his father actually comes from Elympios, and used to be part of Exodus. He left the group when Jude was a baby. That day, Ellen had followed him with baby Jude to the island where Exodus was living, but she had to leave Jude in the care of a villager to chase after her husband. Milla Maxwell, who had come there to accompany the Four on a mission to destroy the Exodus base, found Jude and played with him for a while. He was the one who triggered her awakening as Maxwell due to her strong desire to protect him during the attack on the base. Derek took advantage of the base's destruction to leave Exodus for good, but he kept the truth about his origins hidden from his wife. 
Since his parents were both running the only clinic in town, Jude was often lonely growing up, because they were too busy to pay attention to him. He tried to compensate for that lack of affection by helping others, but that lead to other kids bullying him for being too soft. Out of concern for him, Sonia Rolando decided to teach him martial arts to defend himself, and he and Sonia's daughter, Leia, became good friends. 
Following his parents' footsteps, Jude enrolled in Fennmont's Talim Medical School when he was 13.  He was a very good student and the teachers' favorite, which earned him some jealousy from the other students. 
He was set to graduate two years later, but his involvement in Milla Maxwell's mission changed his life.
He met Milla by chance as she was on her way to infiltrate the Laforte Research Center. He followed her and got involved in her attempt to destroy the Lance of Kresnik. That made him a criminal in the eyes of the government, and he had to flee with her to Auj Oule. He was impressed by her unwavering determination, and decided to support her. 
He grew a lot throughout their journey, but his new way of life relied heavily on Milla's presence. So when she died, he fell into depression and lost sight of their goal. He was eventually able to recover thanks to Leia, and decided to pick up where Milla left and find a way to save both Rieze Maxia and Elympios. He went as far as to challenge Maxwell, and was then reunited with Milla. He kept following his own path even when he learned that his way to save both worlds--releasing the schism--would separate him from Milla. 
In the end, he became a spyrite researcher and worked hard to complete the research and have them replace spyrixes, while Milla took care of the spirits in the spirit world.