Claim on property

My father was the owner of a 1700 sq ft house in Salt lake, Kolkata. I have one elder brother, two elder sisters and one younger sister. The house was constructed in 1997 and since then I have been living in it. Also, during the construction I was given power of attorney by my father for all matters regarding the construction. My father died in 2003 without a will. My mother died in 2008. Now, I have received a legal notice from a lawyer on behalf of my brother & sisters that we are all legal heirs to the property and that the house should either be sold and money shared equally or they should be allowed to come in the property. My claim to the property is based on the following:- 1. I have been living in the said house for the last 18 years, regularly paying all taxes based on the verbal assurance of my father that the house would be mine after his death. 2. I have a copy of the power of attorney. 3. I have disclaimer certificates on stamp paper(photocopy) signed by my brothers and sisters. My question is " Do I have a strong case to defend my right on my home and refuse their claims asking them to go to court?"