From the facts narrated by you, it appears that you are a co-owner of the property, in which capacity, generally speaking, you are entitled to three essentials of ownership:
(1) Right to joint possession of property
(2) Right to enjoy the property
(3) Right to dispose your share of the property
If a co-owner is deprived of his property, he has a right to be put back in possession by a suit.
As a co-owner, you also have a right to demand and enforce a partition; i.e., a right to be placed in a position to enjoy your own right separately without interruption and interference by other co-owner.
So, you may have to file the appropriate civil suit for joint possession / partition.
If your in-laws family was residing there on rent basis of Rs. 8000 pm, as you have mentioned, then you must be having proof of the rent paid in earlier months. Moreover, they have said that they have already vacated the premises. But, you say that they are still in possession, so, you should get proof of their being in possession.
If there is a rent agreement and proof of rent paid, etc., and if their possession is as tenant and not as a co-owner, then you may have to file appropriate proceedings to get possession.
If they are staying there on the basis of being co-owner, then you may have to claim your right of being the other co-owner, and may perhaps have to seek joint possession / partition of the property.
So, ultimately, you may have to file a civil suit, if you are not able to sort out the issue peacefully through negotiations.
The police will be able help only if there is an offence committed, such as violence. Police may not be of help in the civil dispute. If police does not take action on a criminal complaint, you have the option to go to the court and file private criminal complaint.
Please consult some local lawyer at your place by showing him details.
Dr. Ashok Dhamija is a New Delhi based Supreme Court Advocate and author of law books. Read more about him by clicking here. List of his Forum Replies. List of his other articles. List of his Quora Answers. List of his YouTube Videos.