Property issues

Hello, I need few clarifications on the Hindu succession act 1956/2005 and recent amendments. A brief description about my problem: My father, pensioner, is having five daughters (all are married) and only one son (myself unmarried). He inherited his share of ancestral property (agricultural fields) in his teenage from my grandfather. Later, my father sold his entire share and invested that money on plots in city. Now, both inherited and also self acquired properties of my father are registered on my mother’s name. Further, I have also partially invested in properties registered on my mother’s name. None of the property is on my father’s name or my name. Recently, one on my brother in-law demanded my parents for his wife’s share of property as per the Hindu succession act and threatened to approach court. Although, my parents have gifted (not as dowry) a small plot worth 20lakhs for every daughter few years later their marriage. Due to mounting pressure from my sisters/relatives my parents are willing to part their wealth equally. My concerns are as follows 1.Can any of my sisters or brother’s in-law or grand children legally claim the rights for property of my parents? 2.If they can claim, can the court order for equal division my parent’s properties? What will happen to the money that I have invested? 3.Is there any law which takes into consideration the money spent on my sister (marriage, after marriage ceremony, etc) and also medical expenditure of my parents which are borne by me? Unfortunately, No supporting documents except hospital bills. My parents have not proposed any kind of Will so far. But, I am reluctant for sharing the property and planning to fight it legally. Your advised is appreciated.