Ending a tenancy

Tenancy Types and Management

I am a new member . Recently my tenant of 4 years moved out and he started a new tenancy with a different landlord ,he did not end this tenancy agreement which continues to be a rolling contract .
His daughter remains in the property with her baby .She wants to take over the existing tenancy but is only 17 years old , she does not have a job and would be seeking benefits.
I think i need to email my original tenant for him to sign an end of tenancy form.
Is there a legal form for the ending of tenancy ? .
I'm unsure as to the legal rights of the remaining occupants in my property as they are not named on the tenancy agreement.
I basically want everyone to vacate the property so i can rent it out to whoever i choose.
Thank you