Can I gain ownership over my late grandmother's home?

A little backstory..
My grandfather and grandmother are immigrants as well as my mother. This post is more for my mother, but because she doesn't speak English and doesn't understand the system very well, I am writing on behalf of her. She would like ownership over her mother's house.My mother was the legal caretaker over my grandfather (died 2007) and grandmother (died 2023). My grandmother was diagnosed with schizophrenia as well as other mental illnesses and was mentally incompetent for the last years of her life. She would repeatedly call ambulances to take her to the ER because of her mental illnesses and they would send her straight home. Over the course of one day, she would call my mother about 150 times (no exaggeration) and abruptly hang up when my mom answered. There was a point in 2021 when she physically attacked my mother as well as her other caretaker who is unrelated to my family. My mother was obligated to quit multiple jobs in order to offer full time care to my grandmother and, because of this, was paid by a government program to legally provide care for my grandmother for full time shifts. My mother took this money and used it to pay my grandmother's other caretaker who would watch over her overnight while my mother went home. This dynamic went on from 2019 to 2023.
My grandmothers condo is right across the street from my home. In fact, my grandmother purposely moved across the street from us in every home we have ever lived in because my mother was her sole caregiver. In 2021, my uncle signed ownership of my grandmothers home to himself without my mother being present and without my grandmother knowing that he took her OUT of ownership of her home. He also added his wife as an owner as well. He was responsible for handling my grandmothers money and using her funds to pay off her mortgage, so nobody asked questions about his need for any paperwork at the time.
My grandmother ended up passing without a will in September 2023. Within an hour of passing, my uncle and his wife informed us that their son (my cousin we can call M) would be moving into the house. We were all too distraught to argue in the moment and decided to ask questions later. Culturally, we throw multiple events in the months following the death of a loved one and held these events in my grandmothers home. During our last event, my mother asked my uncle what they should do with the house and he again informed her that his son would be moving in. My mother's wish was to sell it and split the profits with her brother, but he informed her that he had put the house up as collateral and taken money out of it for himself (my grandmother had paid off about 90% of it). He also told her he combined my grandmothers mortgage with his own.My entire family was incredibly confused by this choice.
We repeatedly contacted my uncle and I also contacted my cousin and informed them that we are not comfortable with him moving into the house (My cousin M never came to see my grandmother and did not know us or her). My uncle's wife told them to ignore us and threatened to call the police on us for harassment if we continue calling. My mother has shed thousands of tears over the loss of the home and we are now not allowed to go into it or near it. I offered my uncle to pay my grandmothers portion of expenses on the home in order to have it signed to me and he continues to ignore us.I am wondering now after online research if there is anything I can do to void my uncle's ownership of the house. My mother confirmed with me that she was not present and did not sign any form to transfer ownership and believes her brother may have signed it on his own, since my grandmother would not have signed away her home and did not have the mental capacity to do so even if she did. Can I prove my grandmother was schizophrenic to the court to have them void his ownership? Is there anything I can do legally? We are in Cook County IL.