Who all are entitled on My Mother's Retirement Funds And Gpf

 I lived in Delhi. Actually recently my mother expired and in 2012 my brother also expired and in 1990 father also expired.. N have 1 married sister in a govt school teacher. N my mother was working in MCD as principal in primary school. Actually the main problem is that my sister in law interfere in my mother's retirement funds and GPf funds. But in GPf nomination forms, me and my brother names only. So want to ask that is my sister in law has a right in my mother retirement and gpf funds money... Thanks and regards.