The family relationship between the Upgraded Original Vampire Marcel Gerard and the tribrid-doppelgänger Alexandria Gilbert.
Marcel knew Alex's family and saved her, Hayley, and Elena when they babies. They also are related via her being married to Klaus and her being the mother to Hope, Miranda, Jenna, and Nik Mikaelson, Marcel's adoptive father, sisters, and brother. They are currently good friends and allies. However, after Marcel's revenge scheme that incapacitated and almost killed off the Mikaelson family, this pitted Marcel and Alex against each other as enemies. Alex chose to side with the Mikaelsons for her daughter's sake. However, in season four, they allied together to stop the Hollow from terrorizing New Orleans and to stop her from taking Hope, Jax, Nina, and Lily away from them. Although they were allies before parting ways when they defeated the Hollow, their relationship was not the way it was until after season five.