How to challenge and wht to do

3 sisters and an eldest brother Elder brother married n has 2 daughters . Sister 1 (late) - 2 sons Sister 2 (late) and unmarred Sister 3 married but no kids....all siblings above 60 yrs. The unmarried Sister2 died and has her properties which she purchased out of her earned money . She was not in touch with her brother's fam last 25 yrs due to some family fued. Not in terms with Sister3's husband and so was not much in connection with their family too. The person whom she was dependent Till death was last sis1 's elder son. But she never wrote any will for her properties. Now after her death, who is entitled to her properties?? Her elder brother dint attend her last rights too. It was only the sis1's elder son and sis3 and her husband did d last rights. Now for the sake of properties , her elder brother and his wife have come. Will they get the property and can we challenge them? Me being the so called elder son's wife. When d deceased was admitted in hospital, her sis3 and husband have taken a thumb impression on a blank paper (we doubt) beCuz they are claiming to be d owner of one of the property. We dont know wht to do sir/mam. Im the wife of the eldest son.. We were the ones taking care of the deceased all d years. But since ahe had not written any will are we not eligible for any?