Refund the deposit or not?

[David Tung]

I have a older couple decide to rent my rental property. They have moved all their stuff on the first day and plan to move in next day. 3 days later, the granddaughter who has helping her grandparents to find my rental, called me and told me her grandpa passed away, and they decided not to rent the house anymore. We have signed 2 year lease, should I return the deposit in this case?