These young couples have taken over the entire apartment, forcing my uncle to stay in his room and they are not even paying rent. My uncle has been getting sicker and more depressed. We asked some family friends that are close to us to move in instead to take care of him and now these youngsters, who by the way smoke weed and have 2 babies, refuse to leave and are making his life even more impossible. His life depends on them moving out. Thank you.
Your Dad will have to evict them.
This is a length process and not going to happen quickly.
I suggest...your Dad just move. Give the landlord notice..and go. It will be lots easier for the landlord to get rid of them based on a "lease hold-over" than for your Dad to now make the claim of non-payment of rent..or anything else...since he allowed them there for no rent to start with.
Failing all that. Dad needs to get a lawyer to handle this..and quickly.
With neighborhood friends like that, who needs enemies??