Can illegitimate child have right where we don't have proofs

My mother DOB (1959) is the only daughter of my grand father who expired in 1975 by that time my mother was married and all properties are transfered to my grandma and mother, after 30years in 2005 one married lady filed partition suit against my mother claiming that she the daughter of my grand father where she is showing proof of her SSC memo as my grand father is mentioned, and a photo where her mother and my grand father together. Lower court examined the witness produced by her where marriage with her mother was not proven, but lower had given judgement that the she is illegitimate child and equal share to be given, In second appeal district court has cancelled the lower court judgement that marriage was not proven and as per the limitations act that partition suit to be filed before 3 years of property transfer or at the time of sold of part of properties by my mother We are Hindus where as she was Christian by birth and married to a Christian. She filed in high court against the district court judgement. What would be the observations of high court in above case