Just delete one and add the info you want for his wife to the other.
But personally I keep them separate and change the address for her, that is if they weren't living together before the marriage, on her contact to the new address and her last name, that is if she took her husbands name.
They are 2 different people. Even if they are now married.
Add a "Spouse" field to each card. (Add the field, if necessary, Card > Add Field > Related Names. The Related Names field has a pop-up with options such as "Friend", "Spouse", "Father", etc.) If you click on the Spouse field, you get an option to show the spouse's card. Thus, you can link the two cards to each other.