Storyline
Christian is the younger brother of Gregor Mann (Andreas Jancke). During his childhood he had to cope with his mother's suicide and his father's gambling addiction. He was convicted when he took the blame for a crime committed by his father, Wolfgang (Jürgen Haug), who died when Christian was in prison, and after being released, Christian moved to Düsseldorf with Gregor.
He starts dating Nico von Lahnstein (Verena Zimmermann), but breaks up with her and starts a relationship with Coco Faber (Mariangela Scelsi), when he discovers Nico made Coco write love letters to him and sign them as Nico, during a time he was in prison, falsely accused of assaulting Nico's boss.
Later, he meets Olivia's cousin and Charlie (Gabriele Metzger) and Lars' nephew Oliver Sabel (Jo Weil), who moves to the apartment Christian and Coco share with Lars, even if he's not totally comfortable with Oliver's sexuality. Coco starts falling in love with Oliver after sharing a kiss that they keep secret from Christian, but at the same time Oliver develops feelings for Christian during a camping trip to which he was invited by Coco.
When Christian finds out about Coco's kiss with Oliver, he confronts Oliver and accuses him of pretending to be gay in order to get at his girlfriend. On a second confrontation, at the boxing club, Oliver kisses him by surprise. Against his will, and despite being angry because Oliver sent a sports college application for him, Christian starts dreaming and fantasizing about the kiss and becomes confused about his relationship with Coco, and ends up breaking with her. After he admits his confusion to Coco, she leaves for Goa, India.
He talks about his confused feelings with another man on an anonymous chat room, and when he discovers the other man is Oliver (who was unaware that he was chatting with Christian), the confrontation that ensues brings all their feelings to a head and results in Oliver and Christian having sex for the first time. Afterwards, Christian tells Oliver this first experiment convinced him he is not gay, but he still thinks about him and his track entrance trial at the sports college doesn't go well until Oliver shows up to support him.
On a date with co-worker and friend Miriam Christian feels jealous when he sees Oliver dancing with another guy and starts a fight. Oliver manages to stop the fight and accuses Christian of being jealous, and follows him upstairs locked in his room. They both confess their mutual feelings and Christian lets Oliver in and they make love, becoming a couple.
They try to hide their relationship from other friends but it is later discovered by Judith, their flatmate, and Olivia. To Christian and Oliver's surprise, the friends who discovered their relationship are fine with it and promises to keep it a secret.
In the meantime, Christian gets a boxing contract. He fires his first manager, a homophobic man, and hires Gregor, who turns out to be supportive when he discovers Christian in bed with Oliver, but he has to keep his relationship with Oliver hidden due to homophobia in the boxing scene, going as far as pretending to date Judith.
Christian wins his first fight and then comes out by publicly kissing Oliver in the ring, but Axel, the boxer defeated by Christian and who had before mocked Christian for suspecting he was in a gay relationship, attacks Oliver when he finds him alone. The charges against Axel are dropped due to lack of evidence.
Despite an apparent successful recovery, Oliver develops an aneurysm that puts his life at danger as a result of the attack, and most of Christian partners become supportive of them, and the lesion gives the police enough evidence to arrest Axel.
However, some time after Christian's career ends abruptly when he discovers he suffers from myocarditis, which impairs him from doing any kind of professional sport. After a short time working as a park and forest administrator at the Königsbrunn Castle, Stella Mann notices that he has a gift for taming horses, and he starts training at Köningsbrunn as a professional Horse Trainer.
Christian and Oliver's first relationship trouble is caused by Rob, a party planner who is interested in seducing Oliver, and catches his attention by proposing business deals, while secretly attempting to use Oliver's bar, No Limits, as a base for drug dealing. Oliver perceives the suspicions of Christian as mere jealousy, and their relationship is further strained by Rebecca von Lahnstein having feelings for Christian. At the end, Christian and Oliver reconcile thanks to a romantic trip to New York, and Rebecca manages to expose Rob, who is imprisoned.
When Christian suffers an episode of chest pain, and Oliver is not allowed to know any details about him at the hospital as he's not a relative of Christian, Sebastian von Lahnstein suggest both get married to avoid these limitations. Despite some conflict about how the wedding should be, they finally get married, and start talking about adopting a child. After learning that adoption takes up to several years for gay couples, they make an attempt to get known with a lesbian couple, in order to try for in vitro fertilization. However, the other couple demands Christian and Oliver to sign a contract, planning their future activities and decisions to ensure they will always be close to the child, and Christian and Oliver, unwilling to commit to a rigid plan, break up the agreement. Later they start acting as foster parents for Lilly, daughter of a Cameroonian man, during the time he is in prison, and while he looks for a job after his release.
Their relationship takes a turn when Christian and Andi Fritzsche wake up after a party with Jessica Stiehl, who claims both of them had sex with her. This fuels Oliver's fear that Christian might leave him for a woman, and he asks Christian to move out. Christian lives at the stud farm in Königsbrünn for a while, until a fire destroys all his possessions, forcing him to move with Oliver's aunt Charlie, right in front of the apartment in which Oliver lives.
The couple drifts even more apart after Oliver witnesses Phillip zu Hohenfelden being hit by a car and thinks himself responsible, falling into depression. Christian starts an affair with Theresa Erzberger, a coworker at the stud farm, but breaks up with her when Theresa sabotages the training of Dana Wolf. Oliver attempts a relationship with Rafael Velasquez, whom he had met at vacations on Ibiza, and both agree to dissolve their marriage.
Distressed, Christian seeks for relief returning to his box training club and accepts a challenge by a friend of Axel's. The fight triggers his heart condition, sending him to the hospital. The fear of losing him makes Oliver admit that he still loves Christian and break up with Rafael, reconciling with Christian and restarting their relationship. The heart episode severely impairs Christian, since any activity or situation that rises his heart rate would endanger his life. On January 3, 2012 Oliver and Christian got married for a second time in the cabin outside which they first fell in love back in 2008.
In late 2012, Christian is invited to work on England for several months with a worldwide renowned horse trainer.
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