What to do when there is a property dispute

Sir, my younger brother as soon he got married in Feb 12 2018 he started fighting for property .he chased my elder brother,wife and kids away from house. immediately next day mom got stroke and she died and that he became much stronger to fight with dad and unmarried sister for property he never allowed elder brother to visit my father.younger brother demanding to sell the house and give the share because saying my mom gave me the entire house. but still its on my moms name. Dad is not ready to give the house because we both sisters struggled financially to construct the house. and taking care of all expenses till now. younger sis and brother taking care of dad. he was not allowing to visit my dad and sister no these people should take to others without his permission. His inlaws drunk and came to our house with 30 people in the night to give the share of property or else they will file a dowry case against my dad sister and me. no dowry harrasement from elder sis-inlaw for 15 years.