What can be done in matter of ancestral property dispute

Iam woman aged 42, I married on 05/06/1995, my father died on 11/02/2005. My brother died on 06/04 2012, he has one boy aged 18 and my brother wife aged 40. My mother age is 63, I only feed my mother , I look after her medical food needs, my father got house from my grandfather, during partition with his brother so it considered ancestral property . we all live in that house, my father written registered will , in which he stated after my wife death the house goes to son ' s son. Is that correct? If illegal how can I deal this issue? As of my mother got torture from his grandson and son's widow wife my mother wants to give her's portion to me ( I m daughter) if so is that legal , how she may give her part to me in Hindu undivided family act? Since 1989 act, if I m claimed my property in such case , how it divided?. My mother wanted to give her portion of property to me' how can it divideded separated? Now she wanted to write dhanagraiya settlement is that valid?