Dr. Kevin Collins, a psychiatrist, arrives in Port Charles in early 1994 (though he appeared onscreen as early as December 6, 1993) in the hopes of rehabilitating his identical twin brother Ryan Chamberlain. Ryan is a serial killer, and Kevin believes that Ryan is also a victim. Kevin meets Lucy Coe and befriends and counsels her. Eventually, they start dating. However, Kevin needs to deal with his history before moving forward.
Kevin is convinced by Lucy to tell her about his and Ryan's childhood. Their mother was molesting Ryan, and Kevin found out. Kevin decided that he would pretend that he was Ryan to learn what their mother was doing to his twin brother. Lucy sticks by Kevin when Felicia Cummings brings charges of stalking and kidnapping against him. She later drops the charges when she finds out that he didn't intentionally try to hurt her. Kevin begins treatment, and his medical license is suspended.
He later proposes to Lucy. Lucy accepts, and she is also happy when she learns that she is pregnant. However, she miscarries a few months into the pregnancy. They decide to have a double wedding with friends Felicia and Mac.
However, their plans fall apart when Kevin learns that Lucy lied to him about her involvement in the car accident that left Lucy's surrogate daughter Serena Baldwin blind. Kevin breaks off the wedding, but then relents and goes to find Lucy. He is devastated when he finds Lucy in a Florida hotel room with Serena's father Scott Baldwin.
Kevin realizes that he still loves Lucy, but the vampire Caleb plants the idea of doubts of infidelity in Lucy's mind. Lucy has a one-night stand with Ian Thornhart. Kevin and Lucy are once again married, but Lucy is suspicious when a woman named Paige Smith moves in with them in the lighthouse that they were staying in. It turned out that Paige is an angel returning to Earth to finish unfinished business. His former wife Eve is killed in a car accident. Soon after, Kevin is presumed dead. Lucy decides to strive for Kevin's return. Lucy's angel cousin Rafe helped her to rescue Kevin from the other world. In July 2004, Kevin, alongside Lucy, returns to town to attend the funeral of Lila Quartermaine.
In January 2013, Kevin returns to Port Charles at the behest of Alexis Davis, after Lucy had been remanded to Ferncliff Sanitarium following an attack on John McBain. Lucy, having believed McBain to be the vampire Caleb Morley, attempted to stake him with a broken chair leg. Kevin reveals that Lucy's involvement with vampires during her years on Port Charles was little more than a delusion, and that he never had a daughter named Livvie. Around this time, Alison Barrington returns to town, with a teenage son, Rafe, in tow. Seemingly corroborating Lucy's claims about Caleb, it is revealed that not only have Alison and Rafe been on the run for years, but that Caleb is Rafe's biological father. Alison also mistakes McBain for Caleb, and after contacting McBain to meet her on the Pier, she is found dead, having been stabbed to death with a silver arrow that she had given Rafe to defend himself.
Kevin also is in contact with Felicia Jones and Mac Scorpio and they convince Kevin to be there for Lucy. Kevin goes to Ferncliff to help Lucy. Kevin spots Lucy and Heather/Todd trying to sneak out during a worker strike. Lucy blows their cover, but tells them that they need to bring Kevin along. Heather knocks Kevin out. Todd grabs the keys and the three escapees head out. On February 5, he appears again in the interrogation room of PCPD to talk to Lucy Coe with Anna Devane present.
In late March, Kevin comes to tell Lucy Coe that he is heading to Seattle to take care of an patient and will not be present at the 2013 Nurses' Ball. Kevin appears again in The Floating Rib where he sees his wife Lucy Coe hugging her ex-husband, Scott Baldwin. Lucy inquires what Kevin's medical trip to Seattle entailed.
In December 2013, Lucy refuses to wed Patrick Drake and Sabrina Santiago due to the fact that she and Kevin's marriage could be over. He was mentioned to be too busy with patients to spend any quality time with Lucy. Felix DuBois, Elizabeth Webber, and Sabrina convince her to go through with the wedding. In May 2014, Kevin finds out that Lucy has been having an affair with Scott Baldwin at the Nurses' Ball and breaks up with her.
In October 2015, Kevin (again portrayed by Jon Lindstrom) returns to Port Charles for an appointment with Anna Devane. Kevin states that he has been out of the country with his patients and reveals that he and Lucy divorced.
In 2018, he has to call Nora Buchanan from Llanview to represent him when it is revealed he was hiding Ryan. Kevin tells her and Lucy that he is going to plead guilty. He changes his mind to not plead guilty at the last minute. With the help of Lucy, he is able to be released on bail. His bail was already paid and he thought Lucy did it, but it was actually Laura.