How to bypass sister's signature while selling inherited property

My grandfather died in 2005 without any will. My father and his siblings has done a partition deed in 2006 to divide the property among them. My father is selling his property now. My father has 3 kids. I'm the son and two daughters. Do we need to get signature from my sistes during that property sale ?. Are there any legal options where we can skip my sister's signature ?. My sisters are planning to take a huge share by blackmailing that they won't sign.