Before having Harry and Haven, and before James and Lily married, James was in love with a Slytherin named Natalie Rushman, a girl part of the Marauders. But that changed when Lily Evans came into the picture. Heartbroken when she found out James was cheating Natalie left back to the Red Room and no spoke of her since.
Years later the Potters and Lupin-Blacks received an anonymous latter that says they know where their lost friend and past lover was. They jumped at the opportunity, not realizing the consequences that were tagged along.
The Wizarding Worlds reacts to the MCU
*I do not own Harry Potter or MCU. Just my OC's, OC Potter, and the plot*