Greedy family member making us buy our own home. What can we do?

My sister and I are trying to obtain the house we grew up in. Family never got around to doing the paperwork and ended up passing away. Ownership of the house defaulted to another family member who is now making us buy our home at a ballooned price or lose it. Our mother paid for this house already.

By any means Is there anyway we can get our house w/o having to buy it since it was supposed to be left to us anyway?
Added (1). Wow some of your opinions are ruthless and you guys seem to take it personal. People are so quick to judge and assume my sister and I are the greedy ones when there are only bits and pieces of the story here. Or maybe those who seem to be so angry about this are just as back stabbing as my aunt is.
Added (2). I must clarify some things just for my own peace of mind.

My mother and uncle were the only two out of five siblings who helped my grandmother pay the mortgage. My grandmother put my aunt and uncle on the deed way back then and my mom declined to be added at the time.
Added (3). Fast forward 30 years later my mom, sister, and I lived here while everyone else had moved on. My grandmother, uncle, and aunt agreed to sign over their ownership to my mother since she had been living here all those years paying the taxes and insurance, and contributed to the mortgage.
Added (4). Unfortunately before that could happen my uncle and grandmother passed away and ownership of this house defaulted to her. She also inherited two additional houses and bank accounts because my grandmother gave her the right as the eldest to distribute her assets among all her other children. Unfortunately my aunt decided not to do that and kept it all to herself including the house she promised to sign over to my mother.
Added (5). During my grandmother's probate my mother was afraid to speak up and trusted my aunt to sign the house over to her as she promised. Instead she put it in her will to give ownership to my mother upon her passing. My mother spent years taking care of my aunt waiting on her hand and foot and unfortunately passed away.
Added (6). Now my aunt is denying that she ever promised to sign the house over to my mother. My mother was a sweet person who died at the age of 53. She didn't have a will and was used and taken advantage of by family she trusted. She only wanted to leave something of value to her children.

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