John Cates and his younger siblings Michael and Gina were orphaned as children. John was separated from the other two and fell into a rough crowd. He took the street name "Jagger". But he was still a good person on the inside, it just took some loving care from Karen Wexler to bring it out of him.
In 1992, some thugs broke into Kelly's and roughed up the owner Ruby Anderson while attempting to rob the diner. Jagger was one of the thugs, but was shot when he tried to protect Ruby. Ruby forgave him for being involved in the robbery, and gave him a place to live and a job. He started classes at Port Charles High as well.
Jagger started dating Karen Wexler and dated Brenda Barrett for a while too. Jagger located his sister Gina and hired Felicia Jones and Mac Scorpio to find his brother Mike. Mike turned up at a party calling himself Stone. Someone slipped ecstasy into Karen's drink, and Stone rescued her.
After high school, Jagger decided to become a police officer and Karen got a scholarship to study medicine at college. The two became engaged. On the couple's wedding day, Karen's mother Rhonda revealed that Karen's father was Scott Baldwin. After they married, the couple moved to San Francisco where Karen attended medical school and Jagger became a police officer.
Jagger returned to Port Charles in 1995 when he learned his brother Stone was dying of AIDS. He was able to spend time with him before he died. Then, Jagger went back to San Francisco.
Karen returned to town, without Jagger, in 1997 to do a medical internship at General Hospital. She met Dr. Joe Scanlon and fell for him, even though she had a police officer husband back home in San Francisco. Even though her marriage was on the rocks, she wanted to make it work, and tried hard to stay faithful. Karen decided to go back to San Francisco to see Jagger, thinking it would help their marriage and divert her feelings for Joe. When she went home, she found out that Jagger had been having an affair and their marriage was over. Karen then went back to Port Charles.
In 2008, Jagger returned to Port Charles. He had become an FBI agent and was now a single father, fighting for custody of his son named Stone Cates, Jr., after his brother Stone. Jagger's old friend Dr. Robin Scorpio recognized the signs of Aspergers in young Stone, and convinced Jagger to have him tested and to see a therapist. Stone was diagnosed with Aspergers, and Jagger ultimately returned to San Francisco with his son.