Legal status on property matter

my mother had purchased a site in the year 1978 and the building was constructed in the year 1986 the site measuring 62.5 x 40 and building thereon in the ground floor we are totally 4 sons and 1 daughter and iam the youngest in possession of the property since child wood all my brother left the house about 15 years and settled down in there own house the eldest in bangalore and the next on had settled in abroad with gren card status My father expired in 1996 and after my expiry of father my sister elder to me started brain washing my mother to take the entire property and she had asked her to give the property in her name and created difference with my mother and our family (daughter in law) the i filed a injunction suit in 2005 and later my mother declared that she had already gifted the property to daughter 1/2 portion measuring 31x 40 and to take the same after her death later on the injunction suit got decreed in the year 2011 in lower court for 1/2 the property in souther portion and also garage portion facint north for office not to evict me from possession however the case went for an appeal in high court and the same was decreed in my favour as per lower court . later on advise of elders my mother gifted the remaining half portion by way of gift deed also mentioned that she shall be residing in the other half portion till her death later after i got my gift deed registered i came to know that my sister has got the previous gift deed produced in the court cancelled and did another gift deed with addition of measureent of totally 1400 sq.ft kindly advise wheather the gift deed is valid and can other brothers can have a share in the property. I now in possession of the 1000 sqft and the wall is built in between and need to take another 254 sq.ft as per my deed yours jp