Daughter's son's Claim for property share against father's will

We are three brothers and one sister. My father buy a property in 1992 in Kolkata. Measurement of the land is "1 Kattah 10 Chatak 32 sq.feet". My father made a will in the year 2005 under "Barasat District Judges Court". He divide the equal share of the property to his three sons but he didn't gave anything to his daughter. Even he doesn't provide any power to my mother. According to the will my mother can takes shelter untill her dead but she wasn't able to gift/donate/sell/divison the property. My father was died on 24th October 2011 and my sister died on 22nd February 2016. After my sister's death her son claim for the property share of his mother when my father didn't gave any share to his daigWe are three brothers and one sister. My father buy a property in 1992 in Kolkata. Measurement of the land is "1 Kattah 10 Chatak 32 sq.feet". My father made a will in the year 2005 under "Barasat District Judges Court". He divide the equal share of the property to his three sons but he didn't gave anything to his daughter. Even he doesn't provide any power to my mother. According to the will my mother can takes shelter untill her dead but she wasn't able to gift/donate/sell/divison the property. My father was died on 24th October 2011 and my sister died on 22nd February 2016. After my sister's death her son claim for the property share of his mother when my father didn't gave any share to his daughter. My sister's son continue threated us and told us he takes us into the court. Now my query is - 1. Does the claim for property share is actual against my father's last and single will ? (claimed by my sister's son) 2. Can we able to deny his claim for property share ? 3. If he takes us to the court then we have chances to win the case in court ?hter. My sister's son continue threated us and tpld us he takes us into the court. Now my query is - 1. Does the claim for property share is actual against my father's last and single will ? (claimed by my sister's son) 2. Can we able to deny his claim for property share ? 3. If he takes us to the court then we have chances to win the case in court ?