While in police academy, Marc meets Kay Engel and while the two are seemingly enemies at first, they soon become friends. While hanging out, Kay kisses Marc, and Marc begins to get confused about his feelings, especially when accounting for his long-term girlfriend, Bettina Bischoff, who is pregnant with his child.
He begins to have a sexual relationship with him, and the two's feelings for each other begins to grow, causing Marc a lot of confusion and anger. After his son, Benno, is born, he attempts to cut off his relationship with Kay.
After Kay is outed and picked on by Gregor Limpinski, Marc stands up for him, and in the process is hit. While at the hospital, Kay visits him, and while the two are kissing, Marc's mother sees. After visiting Kay's apartment, he tells him to leave, and returns the key.
Bettina leaves after finding out what has been happening, and while at first he attempts to deny it, Marc eventually admits the truth to her. She moves back in, but their relationship is severely strained. Marc also begins to be publicly harassed about his relationship with Kay, however his friend Frank Richter does attempt to stand up for him. Marc eventually attempts to see Kay, and finds his apartment empty, with Kay having apparently left. Him and Bettina split up after deciding their relationship wouldn't be the same again.
Bettina Bischoff (girlfriend; ended)
Bettina and Marc's relationship had been long term, and the two eventually got pregnant together. During Bettina's pregnancy, Marc began cheating on her with Kay, and the two began to fall apart, with her believing there's another girl. After their son is born, Marc attempts to end his relationship with Kay and to stay loyal to Bettina and their family, however he eventually is caught cheating with Marc, and the two split. After he admits the truth to her, they briefly try again, however they end their relationship again after agreeing it wouldn't work out.
Kay Engel (in love with; ended)
Marc and Kay initially started off disliking each other when they attended the same police academy, however after they begin talking, Kay offers to help Marc improve his running. While they were running, Kay kissed Marc, later claiming it as a joke. Another time when running,