Power of attorney?

my grandmother gave my mom power of attorny,shortly after our house cought fire(i was living in this house with my grandmother at the time for about 6yrs.),any way the house was rebuilt with the promise that i would be renting it when it was completed & granny would be staying with my mom.to make a long story short,one day before i was to move in my now x parents show up talking about the house will be sold & that they have a buyer(that was bullshit)no buyer but the house is up for sale but no takers.my granny says for me to move in thats what she wants(& no she's not crazy yet ).what options do i possably have to fight my GREEDY *** SO CALLED X PARENTS?or do i even have a leg to stand on?PLEASE SOMEONE TELL ME SOME POSITIVE INFO I COULD USE IN MY DEFENSE.... THANKS; ELMO