People in a relationship, Your partner either has amnesia and no memories of you or you have an alternate version of your partner who has those memories.
In the first scenario, your partner is the actual one you have now. They are the same person you experienced everything with. They have no memory of you existing, but remember everything else. If children are involved, your partner's fake memories are of being a single parent. You can show them proof of your marriage and convince them to grow a life with you but they would do it from a blank slate. There is no chance of the memories returning.
Alternatively, your real partner moves on and is replaced by one from another dimension. This partner has all the memories your real one would have had before the amnesia. In this scenario, any children, family members and friends would be unaware of the switch, unless you told them.
Which would you choose?