Siblings on lease and one is leaving

[Lorenzo G.]

Looking for some advice:

Currently renting m2m to a brother and sister - brother let me know that he will be moving out in about a month. They’re both on the lease.

Do I return the security deposit and have the sister come up with the full deposit and put together a new lease m2m? I believe her boyfriend will be moving in so I will need to do a background check on him. How do I handle any damage when returning the current security deposit?

They have been great tenants and always pay on time

Thank you!