There were addendums that allows us to be added/removed. The lease that the rental agency sent was the oldest lease (that the guy paying the rent) signed first when he first moved in. The rental listed on there is about 6-7 years old. Since that lease expired they've been utilizing the addendum to renew lease, add new lessees (like us) and etc.
Edit: addendum was called "Lease amendment, extension/change of terms"

