Brother sent notice for partition of property

I need a clarification from you. My father is a retd. govt employee (retired 8years back). he has three sons only, which I'm the eldest. i'm a private employee. the other two brothers are govt employees and we three got married and have children. two years back my mother expired owing to ill health. now the younger brothers have sent a legal notice to my father asking him to divide the property into four parts. but daddy (as he himself lacks his left hand), with my suggestion married and i advised him to keep the property for h