My question involves landlord-tenant law in the State of: New Jersey

Hello,

We rented a house apartment to two brothers. They signed a month-to-month leash for only two people. The rent is $1000. Last Winter, the older brother kicked his brother out and moved his friend in. And now his cousin is living in the apartment with the two of them. The cousin has mail and packages delivered to our house under his name. The cousin has been living in the apartment for 4-5 months. We spoke to the older brother and told him that the apartment is only for two people and if he wants his cousin to live there, he has to pay rent. Do we have the right to ask his cousin to pay rent? If so, how much rent should he pay?