Can a mother transfer a property by will to his grandson?

Hi, My father who is the owner of self acquired property transferred his home in the name of his wife (my mother) who is a housewife.. my elder brother has taken a loan of 20 lacs with my mother as co-applicant for construction of that house. Me n my elder brother both are paying the EMIs in equal share. Hence, even if the loan is in the name of mother ( in whose name the property is registered) and my elder brother.. the EMIs are paid by me n my elder brother. Now the problem is, my mother intends to transfer the house to his grandson (son of my brother brother) by way of WILL.. leaving me out of that.. is that possible.. the loan is of 20 years which is just started.. can my mother make any such WILL while i am also paying EMIs along with my elder brother..even if i am not the applicant of loan.. i am very tensed.. my mother has emotional bent towards my elder brother and his family.. in that situation what can i do.. i have no other home than that and my brother is working as senior manager in a reputed mnc. Is that possible that my mother can make such will while the property is under loan and exclude my share wothout my consent? If yes, is there any law bu which i can claim my right in that property? Plz help..