How to proceed with sale of jointly held property

Property in grandfather(mother's father) name, he died 40 yrs ago after that it come to grandmother she also died in 2010. She before dying made will that property be distributed in 3 equal shares one to me her grandson, my uncle(mother's elder brother), my aunt(mother's elder sister). I and my uncle want to sell the property but aunt is creating trouble for both of us by taking objections in property sale even though she gets her share of money after sale. She is not prepared to buy the house from both of us. She is not agreeing even for transferring the property ownership from grandfather's name to living survivors names.The house property original papers are lost, we both explained to aunt to come to sign for duplicate papers in society meeting, she's not agreeing for that too. The will of my late grandmother clearly states if 2 parties are agreeing they are in majority therefore 3rd party will have to agree. I and my uncle want to sell property urgently but don't know what to do