Miss Martian and Superboy (real names M'gann M'orzz and Conner Kent) are the main couple of "Young Justice".

Miss Martian and Superboy first met when they both became founding members of the Team, a covert group of the Justice League's protégés. They were both strangers to Earth as Superboy is a hybrid clone of Superman created by Cadmus to be used as a weapon while Miss Martian is the niece of Martian Manhunter who secretly stowed away on his last trip from Mars in the hopes of better life for herself. Miss Martian and Superboy quickly developed romantic feelings for each other and gradually begin to grow closer throughout the first season when they begin living together at Mount Justice, working together on missions and later attend High School together. Miss Martian and Superboy's feelings each other grew stronger to the point they eventually came to develop a strong psychic bond and connection. However, they both had trouble admitting their true feelings as Miss Martian was shy and nervous while Superboy still hadn't fully realized his feelings while at the same time, they were also the object of unwanted attention and attraction of Kid Flash and Artemis.

Eventually, during an uncover mission in Belle Reve Penitentiary, Miss Martian and Superboy finally became a couple, but decided to keep their new romantic relationship a secret from their teammates and found a balance, making sure their romance does not interfere during missions. Gradually though, everyone comes to learn and accept their relationship, but it would soon face its first challenge when they both began keeping secrets. Superboy discovered Lex Luthor to be his human father and began using Shields to access all kryptonian powers while Miss Martian is revealed to be a White Martian and was being blackmailed by Queen Bee. By the end of season 1, however, Miss Martian and Superboy's relationship became stronger when they both confessed secrets, further strengthening their relationship with not only each other, but their teammates. Since then, they maintained a strong, stable and serious romantic relationship over the next five years.

However, shortly before the beginning of season 2, Superboy broke up with Miss Martian when she began abusing her powers by psychically attacking the minds of her enemies and left them in catatonic states. Superboy became angry with Miss Martian, especially when she refused to acknowledge the wrongful use of her powers as she believed her actions to be justified. Superboy hoped he would eventually managed to get through to her until Miss Martian finally went too far. In an effort to save their relationship, Miss Martian decided to tamper with Superboy’s mind to make him forget he was ever upset with her. However, Superboy was not effected, but was left deeply hurt and betrayed by her actions, but was especially heartbroken that she was willing to use their special psychic bond against him, leading Superboy to break off their relationship.

Following their break up, Miss Martian and Superboy’s relationship becomes strained, but they manage to maintain professional when working together on the Team. Miss Martian also begins a new romance with Lagoon Boy. However, it clearly shows that despite her new relationship and their breakup, Miss Martian and Superboy are still very much in love with each other, but simply try to ignore and hide their feelings. Eventually, Miss Martian finally came to realize the error of her ways after attacking Aqualad and by the end of the season, she breaks up with Lagoon Boy and works on reconciling and restoring her relationship with Superboy.

Two years later in season 3, Miss Martian and Superboy have gotten back together with their relationship fully restored and stronger than ever as they now live together in Happy Harbour. Recently, Superboy proposed to Miss Martian in the season premiere and they are now engaged to be married. However, they soon find themselves housing new young heroes in the aftermath of separate missions, preventing the couple from spending quality time together. Despite their new arrangements, Miss Martian and Superboy's romance stays strong and eventually after the new heroes move out and join The Outsiders, the couple finally begin to truly enjoy their engagement.

However, towards the end of the season, Superboy learns the truth about Miss Martian’s involvement with the Anti-Light team and their actions, upsetting him and believing them to be no different than her actions from the previous season. The newfound strain between them leaves their relationship and engagement into question for sometime. By the end of the season, however, Superboy apologizes to Miss Martian for bringing up old wounds and comes to understand she was forced to make hard decisions. Superboy reassures his love for Miss Martian, revealing he can't ever imagine his life without her and the couple seal their reconciliation with a kiss, once again restoring their relationship.

In Season 4, one year has passed and Miss Martian and Superboy are finally getting married. They are traveling to Mars to have a traditional martian wedding ceremony with M'gann's family with Beast Boy and Martian Manhunter joining them and plan to hold an official ceremony once returning to Earth. However, the bride and groom quickly discover racial problems on Mars have worsened and escalated since their last visit and are upset to learn many martians, including most of M'gann's siblings disapprove of Miss Martian and Superboy's upcoming wedding. Despite the problems, however, Miss Martian and Superboy's love for each other is stronger than ever as they are excited and happily await their wedding in a few short days. However, unknown to the couple, they are secretly being followed by members of the future Legion of Super-Heroes, who are trying to protect Superboy in order to save their future.

Unfortunately, tragedy strikes when Superboy discovers a virus bomb planted by Miss Martian's young brother to kill off every Green and Red martian. Superboy heroically sacrifices himself to save the martian population, but was apparently killed in the process, discovering too late the bomb had also been laced with Kryptonite, leaving Miss Martian deeply heartbroken and devastated by the loss of Superboy. Miss Martian hunted down and finally confronted her brother, determined to seek vengeance for Superboy's death, but is shocked to discover M'comm is not the true culprit. The discovery leaves Miss Martian further heartbroken and grief-stricken than ever, realizing Superboy's true killer is still out there, but no longer have any leads or suspects to who was responsible.

Miss Martian's grief over the loss of Superboy caused her to close herself off both emotionally and mentally, but with with the help and support of her older sister, Em'ree, Miss Martian begins to open up and express her grief over Superboy's death, admitting she doesn't know how she'll be able to go on without him. However, unknown to everyone, Superboy is revealed to be alive, having been saved by Phantom Girl who managed to transport them both to the Phantom Zone, but ended up leaving them trapped in the process. Superboy is determined to find a way to escape the Phantom Zone in order to reunite with Miss Martian, but later begins to to develop Zone Sickness, causing hallucinations and amnesia and later falls under the influence of General Zod. Despite everything, Superboy still remembers his love for Miss Martian as his last shred of hope.

Eventually, everyone finally comes to learn Superboy is still alive. The original Team learn of his survival after uncovering the mystery and conspiracy behind his disappearance, but keep their investigation hidden from Miss Martian. However, Miss Martian finally learns Superboy is alive upon meeting Phantom Girl, who managed to escape the Zone and informs her of the situation. Miss Martian is determined to do whatever it takes to save Superboy and altogether, the heroes unknowingly enact separate rescue missions to free him from the Phantom Zone and the Zods. During the final battle, Miss Martian successfully manages to restore Superboy's mind, reuniting the couple at long last after a whole season apart and work together to defeat the Zods once and for all. By the end of the series, Miss Martian and Superboy finally get married with all their friends and family present in a special wedding ceremony in their home of Happy Harbour, at long last finally becoming husband and wife.