Need advise

My father-in-law has 3 Sons & 2 daughters. 2daughters got married and settled in past (20 years ago).I'm wife of 2nd son.My father-in-law was died without partioning (5acrs) property.  My mother-in-law gifted the property to 1& 2 sons. My mother-in-law died. After 10 years 3rd son and daughters are claiming partions in that property. What should we do?