Can a registered will be challenged in Probate Court?

My father passed away in 1998 and mother passed away on 2017.He had a house in Delhi given to him by Government of India as refugee fro Pakistan (not self earned ??).House was renovated after his retirement from his retirement funds.The will made by my father before his death was registered but the witnesses are dead/not available.As per will he left all his property in the name of my mother (now expired) and my brother but for me he made a provision to stay in the house if I am in need. I was a working woman till my retirement and have my own house and savings to survive. At the time of making Will there were many family problems. After marriage I was settled in Mumbai. I have a strong feeling that the will was made under great pressure and with upset mind. I can say this because I know my father very well and he raised me with lots of love, dignity and always treated me and my elder brother equally. He treated son and daughter in the same manner and always equally. So I can say with full confidence that he made the will under some pressure.and I hereby decide to CHALLENGE the Will. My mother managed everything by herself till her death. All utility bills like electricity, water and land tax etc were in her name and paid by her. As per her knowledge my brother and his family informed her that the house is in her name. Even we were all kept under the impression that the house is in my mother's name and that the house Title is changed in my mother's name as per my father's Will and wish. My mother always wanted to keep both her children equal and her wish was to give both children same and divide the house floor wise. But my brother and family never supported her and never honoured her wish. I was emotionally fooled/manipulated by my brother and family. He came to me soon after my mother's death with documents and in sad state of my mind I signed NOC on stamp paper (but not registered) and receipt for what he gave me.My mother did not leave any will as per my knowledge. Now they have applied for Probate of Will of my father in Delhi Court in which I am a respondent. I am looking for a trustworthy lawyer to take my case and help me fight for my rights and fulfil my mother's last wish. Do I stand a chance to get a favourable decision by Probate Court.