Based on my research, I think the answer is that
1. You have to file MFJ
2. Each person will be assigned 50% of the total income regardless of when you were married
3. Then the person that receives the subsidy, using a family size for themselves and any dependent they have WITHOUT the "new" spouse . It will have it recalculated using the 50% of Joint income for the months prior to marriage (if you are married in Nov, then you put 11 on line part 2 Form 8962). Depending on this answer, will determine how much subsidy they should have received and that will determine
how much subsidy is to be repaid.
This is the ALTERNATIVE calculation for year of marriage option Form 8962
There is also another case whereby each person was receiving a subsidy and then gets married, then you assign 50% of the MFJ income and can allocate the subsidy they would each receive individually.
That is my understanding.
