James Nathan Reeves is the biological son Liesl Obrecht, but was raised by his aunt Madeline Reeves alongside her daughter, Nina Clay. He is trying to take down Dr. Silas Clay, whom he believes put his "sister" in a coma. He is going by his middle name and the maiden name that Madeline assumed, so Silas won't know the connection. He is stated to be a lot younger then Nina. While in a jail cell next to Madeline, Obrecht asks how James is, and she reveals that she is his mother.
Nathan arrives in town on New Years Eve. He is seen is at Maxie Jones's apartment door and we learn that he will be subletting Maxie's place while she is out of town. Maxie and Nathan share a brief discussion about making a fresh start in the new year and past mistakes, before Maxie leaves for the airport. After Maxie leaves, Nathan starts to settle into the apartment. He then makes a phone call and it's discovered that he is the police detective from New York that has been hounding Dr. Silas Clay and Ava Jerome, and he knows their secret.
He continues to hound Silas and Ava with calls and texts, but they both ignore him. He then goes to see Commissioner Anna Devane at the Port Charles Police Department, because he wanted to be hired on as a detective in Port Charles, so he could pursue the suspects in his case. He initially says he wants to work in Port Charles to help bring down the Jerome mob family that was trying to move into the city. He then tells Anna about the Silas and Ava case, without revealing all of the reasons why he is so intent on closing this case. Anna decides to hire him at the PCPD and is assigned to be Dante Falconeri's partners, but makes it clear that he must tend to his regular duties first, and the case that brought him to town would have to come secondary. Later, Nathan goes to the hospital to confront Silas.
Silas is evasive toward Nathan's questions and refers Nathan to his lawyer, Diane Miller. This prompts Nathan to pay a visit to Sam Morgan, Silas' girlfriend, and he reveals to her that Silas has a wife. Silas showed up at the police station a day later, unhappy with the fact that Nathan spilled his secret to Sam, and finally agreed to talk to him. While questioning Silas about Nina's overdose, Nathan reveals that the anti-depressant Nina overdosed on was prescribed to Silas and not Nina. After questioning Silas, Nathan also brings Ava into the station and questions her on what she knows about the situation.
Nathan's investigation into Silas and Ava is put on hold when Carly Jacks is kidnapped. He begins working with his new partner, Dante Falconeri to solve the case and find Carly. While on the case, he unknowingly meets Dante's wife, Lulu, when he goes to Carly's house to collect evidence. Nathan turns out to be Madeline's son James Reeves. He changed his name when he joined the police force in order to become the head investigator in his sister's case. Madeline isn't too happy about Nathan's career choice but wants him to prove once and for all that Silas is guilty and after Nina's money.
On April 7, it is revealed that Madeline was the one who killed Nina but she didn't mean for Nina to die, she wanted to kill Nina's baby. On April 8, Nathan arrests his "mother" for murder. On April 14, Madeline tells Nathan that Liesl is his mother and Britt is his sister. On April 30, Nathan tells Britt that they brother and sister.
In June of 2014, Nathan lied to a judge and said that he threw Maxie's custody hearing summons away. He also reunites with his not so dead sister/cousin, Nina. On the day of Patrick and Sabrina's son's funeral Nathan and Levi get into an argument and Levi punches him. He is later called to be a part of Maxie's custody hearing and it is revealed that the judge found out that he lied. Nathan told judge that he didn't lie so the judge asks him testify under oath but before he can Maxie stops him and admits that he lied for her.
Maxie is later denied custody and visitation rights again. After the hearing Nathan accuses Levi of telling the judge (which he did) but he denies it. Maxie chews Nathan out for accuses Levi of telling the judge. A couple of days later, Nathan arrests Levi for trespassing on the Waterfront property which ends and when he tries to arrest Maxie they end up handcuffed together. On July 3 (the 4th of July on the show), Nathan and Maxie walk home but along the way they fight and watch the fireworks.