Respected Sir/madam

My father had purchased a revenue land in 1990 from a GPA holder. My father becomes the second GPA holder. He built the house and we are leaving their from past 20 years. My father expired recently the property is not registered, now It comes under BBMP, for paying tax everything the property to be registered, please guide me can my mother make a gift deed of the same. Or please help me in solving this problem. we are not financially strong and we don’t know where the 1 GPA holder is . and if go for land lords grand children they ask from more money we can’t offer. Please guide me.