Unless you have an employment contract which guarantees or protects your employment, you are an employee at will. An employee at will may be fired at any time, for any reason. So without an employment contract, if a company doesn't want to employee two spouses, it would be free to fire one (or both) of them--companies have almost free reign to make their staffing, hiring, and firing decisions and policies, subject only to a few limitatios, like no illegal discrimination on the basis of race, sex, religion, age over 40, disability, etc.