Jonathan arrived as an unnamed stranger looking desperately for Ryan Lavery. He was shooed away by the Fusion girls -- except for Simone, who flirted shamelessly with him. He eventually stumbled across the path of Kendall Hart, who was also taken with Jonathan. She seduced Jonathan and arranged to have Ryan walk in on her and Jonathan having sex. When he did, it was revealed that the stranger was actually Ryan's little brother.
Jonathan apologized profusely for having slept with Kendall. Ryan quickly forgave his little brother, saying that Kendall was really the one to blame. The two brothers caught up, filling each other in on what had been going on since they last saw each other many moons ago. Ryan offered his law-school-graduate brother a job at Fusion. After Jonathan botched an attempt to acquire a biotech company for Cambias, Greenlee discovered that Jonathan had lied about his past -- he had dropped out of law school. Greenlee gave Jonathan a chance to come clean with Ryan, but when he refused, Greenlee spilled the beans. Surprisingly, Ryan was very calm, and allowed his brother to continue working at Fusion and Cambias.
On the personal side, Jonathan crossed paths with Maggie Stone and the two started hanging out. They became lovers, but Jonathan was having horrible mood swings. He would get angry for no reason, and that anger eventually turned to violence. He and Maggie became engaged, but after one too many blows, Maggie left Jonathan. It wasn't long before Jonathan spiraled completely out of control and kidnapped Greenlee and Lily, and later Kendall, holding them at a cave not far from the body of his brother, Braden -- whom Jonathan had claimed was the one who made him stalk Greenlee for many months. Jonathan was believed dead in the explosion at the mineshaft, but turned up alive and well-and completely delusional-in Nova Scotia with his sister Erin.
Medical tests showed Jonathan to be suffering from a brain tumor. After the tumor was removed, a kinder, gentler Jonathan emerged, who was nothing like the person he had been before. He seemed to regress back to being a child. Jonathan was determined to return to Pine Valley to right the wrongs he had committed, but the citizens of Pine Valley weren't very happy to see him. He soon embarked on a friendship with Lily Montgomery, who had autism spectrum disorder. The two began dating, but Jack, who didn't want his daughter anywhere near Jonathan, sent Lily back to her special school. Jonathan eventually managed to hunt Lily down, and the two married in New York before returning home. In New York, Jonathan had begun suffering from severe headaches, and after returning to Pine Valley, Jonathan ended up in the hospital, where he soon realized that he was back to 'normal.' Erin realized the truth, as well, but Jonathan begged her to keep it hidden, determined to remain at Lily's side. When Jackson overheard Jonathan and Erin having a conversation, Jack realized that Jonathan was no longer impaired. Jackson tried to have Lily declared incompetent so that he could have her marriage to Jon annulled. Jonathan couldn't bear for Lily to be declared incompetent, so he called a stop to the proceedings. Jon told Lily the truth about his recovery, but Lily could not bring herself to forgive Jonathan.
Lily went online looking to meet someone who "matched" her, and was duped by Terry, the violent sexual predator Jonathan had saved her from in New York City, posing as "Asperger Boy." Lily agreed to meet "Asperger Boy" and soon found herself in danger. Fortunately, Jonathan found Lily and saved her from Terry, who was poised to rape Lily. That heroic act earned Jackson's respect for Jonathan, but Jackson's approval came when Lily no longer wanted anything to do with Jonathan.
Amanda seduced Jonathan and they began a "no-strings" relationship, one that Jonathan ended when he realized that Amanda's heart was engaged. Jonathan and Amanda remained friends, and it was Amanda who helped Jonathan through the aftermath of his beloved sister's death. Losing Erin shattered Jonathan's world, and he mourned fiercely.
Ava Benton, Lily's look-alike half-sister, came to Pine Valley. Jonathan was initially wary of Ava, and feared she would hurt Lily. Upon gaining some insight into Ava, Jonathan began to see Ava in a different light. Jonathan and Ava initially fought their attraction to one another, but finally gave in and made love.