Dispute between me and my father

Hi, I am 31 year old woman and born with two elder brothers to my mother. My mother died in an accident when I was 15 and my father remarried and got one son to his second wife. Now my father wants to donate his properties to every one but not on equal basis. Being a woman, I will get only small portion and the rest is being given to my own brothers, my step brother and my step mother.when I checked with my dad regarding such partiality while donating his properties, he told this is how his relatives did in the past. All his properties were earned by him and claims he can do as per his wish. I heard he would require my signature in all the deed documents for donating his property to us and my father is also asking me to sign while executing the deeds. My question is if I dont agree to sign, can my father still donate as per his wish. How to get my deserved share in this case.