Who is responsible for next month's rent?

[Jon Wiese]

My son and his wife have been renting a house from me for about 6 mos. They are renting without a lease, month by month. They are now in the process of getting a divorce.  I gave them 30+ days notice that they must move out.  My son moved, however his wife will be in the house for the next 30 days.  No rent will probably be paid.  Which party is responsible for the upcoming month's rent - the wife who is occupying the house, or both of them?  They live in Kansas.