Duplex - moving upper unit downstairs to lower unit

[Kham Sing]

I have upper unit tenants moving to lower unit. The current situation  is they have three adult, great uncle and great aunt, with their 23 year old grandson. I have only sign the lease with the great uncle and great aunt but not with the grandson when they move in. The problem are:

1. The grandson and another friend wants to sign a lease for the upper unit, but has not send me the application yet. The family are due to move out by the end of the week. 

2. Grandson friend may be staying over night with them as of right now during the transitioning, but not 100% sure.

3. Without the permission of the great uncle and great aunt, he consistently inviting friends over, drinking beer with them, and perhaps smoking weed indoor. Policy say no smoking/what so ever. I'm just assuming about the weed part because of the smell. 

So I am asking for help to how the best solution to transition everyone downstairs. I believe the grandson and his friend probably not qualify that's why they did not give me back the application yet. And how do I ask them to move with the great uncle and aunt legally and address the other problems I listed above.