Q: Can us tenants be evicted if my baby sisters dad is staying with us but isn't on the lease?

My mom has been letting her boyfriend stay with us in our apartment. Our landlord said that he did not want him staying with us because he is not on the lease and it is illegal. He also stated that if he did not want to leave or we did not want to obey him he was going to give us a 30-day notice to move us out.

A: 

Basically, your landlord may ask you and your mother to vacate for a violation of the lease that is not corrected within 3-day, or by providing your mother with proper notice under the law (30,60, 90 days depending on your circumstances). Your landlord does not need to provide any reason for a 30,60,90-day notice to vacate.

Your lease may address the issue (e.g. people who not a party to the lease may not stay in unit more than 2-weeks "visitors"). Many leases permit a non-party to the lease to reside in the unit by paying an extra fee (e.g. $200/month.)  It is important to know whether your mother is violating a term of lease by having her boyfriend reside with you.