see this previous post:
On the "Person/Details page/screen ...
Go down towards the bottom of that page/screen to the "Family Members' Section ...
Then, on the 'second' line under the "Family Members" Title, you will see "Add Spouse" (which is a 'Button'/link access), select that; and, then, add another Spouse (in fact, you can do that as many times as is needed).
I hope this helps.