Sounds like you are a tenant. They have to go thru the eviction process. As a tenant at will, they will ultimately prevail, but if done correctly starting today, you wouldn't be in court until mid-September.
To questioners from West Virginia & New York: Although I am licensed to practice in your state, I practice on a day-to-day basis in Massachusetts. I answer questions in your state in areas of the law in which I practice, and in which I feel comfortable trying to offer you assistance based on my knowledge of specific statutes in your state and/or general principles applicable in all states. It is always best, however, to work with attorneys and court personnel in your own area to deal with specific problems and factual situations.
Self help evictions are illegal in Massachusetts.
The property owner (your grandmother) or her agent (your father) can evict you but only after legal notice. See the link to Mass Legal Help's Housing section below.
You are a tenant at will, so you are only entitled to 30 days notice, 14 days if he is claiming non-payment of rent. But even a properly served notice does not give them the right to lock you out. You may have defenses to raise or the possibility of seeking more time to find a place to live, if you do get back in until they take you to court properly.
If you can afford an attorney, you should hire a landlord tenant lawyer to help you get back in your home until you have a chance to find a new place. If you cannot afford a lawyer, use the Find Legal Aid link below to find the Greater Boston Legal Services intake line or a lawyer referral service.
I have changed the subject of your question to Landlord Tenant so that you might get answers from local LT attorneys.
NOTE: This answer is made available by the lawyer for educational purposes only. By using or participating in this site you understand that there is no attorney client privilege between you and the attorney responding. This site should not be used as a substitute for competent legal advice from a licensed professional attorney in your area who regularly practices in the subject matter which your question is about. You should develop an attorney client relationship with the lawyer of your choice so that your communications will be subject to the attorney client privilege and have the other benefits of a professional relationship. The law changes frequently and varies from jurisdiction to jurisdiction. The information and materials provided are general in nature, and may not apply to a specific matter as partially described in the question.
To remove you properly, they would need to go through the proper eviction process. Be sure you don't give them any reason to call the police. Best of luck.
Criminal Law (all misdemeanor & felonies in District and Superior Courts), Drunk Driving and Drug arrests, Sex Offenses, SORB, Crimes involving Violence or Theft, Domestic (Divorce, Child Custody, Alimony and Child Support) and Family Law (Modification, Contempts & Paternity), Juvenile Law, Domestic Violence and Restraining Orders, Business Law, Personal Injury claims, Probate Law (Guardianships, Conservatorships & Estate Administration) and Legal Malpractice. For these and other areas, contact me. NOTE: This preceding message DOES NOT create an attorney-client relationship. It is not a protected or confidential communication. The statements made herein are not to be interpreted as representations or warranties of any kind. No reliance should be placed on the statements made herein. It is recommended that the recipient(s) should undertake their own research to reach their own opinion. The writer does not accept professional responsibility on this matter. TO CREATE an attorney-client relationship REQUIRES a signed retainer/fee agreement along with a retainer fee that must be received by my office.