A is famous but no one actually knows his identity, I'm thinking he hides his identity somehow like Sia or Marshmello or works under a pseudonym like Banksy maybe? B has no idea their partner is this famous person until a fan/paparazzo/innocent bystander happens to reveal the identity of A to the public. I want this to cause a lot of stress on their relationship. Maybe A didn't tell the truth from the beginning because he didn't want the uncertainty of B staying because of the fame, leaking the truth to the public, leaving him or any other reason really that just spiraled out of control for A. B is upset over A lying to him for years, and also they are both suddenly thrust into new life where people hound them for interviews, pictures, autographs and some even question if B is a gold digger, good enough for A, hot enough, smart enough etc.