validity of will

My mother died in 2011. My brother and his family was living with her in a property owned by her. We live in another city. After 8 months of her death, my brother announced that that he found a sealed envelope which may contain a will. We decided to meet within next 3 months and the envelope was brought out by my brother. to my surprise, it was a stapled envelope, there were no seals. I was further surprised to note : 1 It was a typed document in English- a language mother was not used to. She used to correspond in Hindi. 2. As per said 'Will' her entire property and cash was 'Willed' to my brother alone. 3.This Will was witnessed by two persons, both confirmed that none read the contents, nor did the testator sign in their presence. It had her sign already. The two witnesses signed the Will after a year of the date written on the wIll and both signed on different days, not in presence of each other. 3.The envelope also contained a previous Will in Hindi in which she had bestowed the property between three children. My brother inssited that since the english will is last, it is valid and the previous one in Hindi is superceded. 4.Neither will was registered. Is the Will in English valid , specially when during the last few months of her death she regularly made it clear to many relations that she wants to distribute her property equally amongst all children? It appears my mother has been misled to sign on the document without realising the contents of it. How to proceed to challenge the 'doubtful Will' and get justice?