Before becoming a Robot.
During the Great War between the animal Mobians and the human Overlanders, Jules and his brother Chuck
were on patrol and came across a defect Overlander, Julian Kintobor
. It was Jules' idea to rescuing the Overlander and taking him into their side of the war. Becuase of this, Julian's knowledge help won the war for the Mobians' favor. But Jules suffered mortal wounds from comabt. Chuck decieded to test his roboticizer, a machine that turns people into robots, on his brother inorder to save him, only to find that his machine worked too well: Jules lost his free will, thanks to Julian's tampering to the machine.
The Last Robian
Shortly before the Xodra's attack, the alien spieces, BEM, managed to take all of the Robians on Mobius and brought them back to normal. All except Jules.
During his time in space, Sonic found out that if the BEM would ever return Jules to normal, his wounds prior to him being roboticized would kill him. Jules accepts this as now he can enjoy being with his family, even though everyone else was normal.
Being a Father
There have been times that Jules manage to help his Sonic. The first time was when he protect his son from a robotic imprianstor of Tommy Turtle, one of Sonic's childhood friends, was about to kill him in his sleep. The robot manage to fataly injure Jules by forming his hands into drills. Sonic manage to save him with a Power Ring. Jules was also was infected by A.D.A.M.'s nanites, that forced him to take Tails to the corrput A.I. and have himself slef-destructed,
though Jules handed ADAM Tails, he mange to prolong his self-destruct program long enough for Sonic to beat ADAM and Jules regain control. He even faced Scourge, the Anti-Sonic, in the middle of the night and had a 'Father-&-Son' Talk and even made Scourge leave.