Does a Will override my uncle having my grandma (93) sign over her land/house?

My Grandma/Grandpa have a house and 10 acre's. My Uncle was going to buy my Grandpa a truck if you would sign over his land/house, Grandpa said NO way. Now my poor grandpa has passed and my Grandma moved in my Uncle's house, she gets a check per Month not sure how much, My Uncle had my Grandma sign over land/house at the age of 93. There are a total of 3 Siblings involved, in the Will it is suppose to be divided by the 3 siblings. Uncle thinks because Grandma lives in his house he should get ALL ! :( He does use Grandma's money and Uncle still works full-time. He hires a cheap caregiver to come in take care of her and clean his house while he is at work. He does use Grandma's money for that also. He writes checks out to cash. Pays caregiver cash under table. I feel Uncle is stealing. Does a Will over-ride on what Uncle has done here ? Uncle is the Power of Att. over Grandma. I feel like this elderly exploitation abuse ? what are your thoughts ?