My ancesstors(chacha) property is given to somebody else...what should i do?

Sir, my chacha ji expired few years back so his property (ancestor) went to his wife. They didnot have a child. now my chachi ji is also expired...and she has made a "will" that their property should go to her brother's children....can she do that ? because its my chacha ji's property and infact my grandfather's... one more point ...my chacha has a adopted girl.....she has been given nothing in the "will".. plz suggest ....who should be the owner....