Need advice about how to deal with rogue relatives that keep causing problems.

Hello, recently I inherited a house that belonged to my late grandmother by an "Irrevocable Inter Vivos Deed of Gift” in which she prepared and had notarized by 2 notary witnesses. One month prior she amended and restated her trust, revoked the original POA/Trustee and appointed me the new POA/Trustee through an attorney she hired to help her properly make these changes. The amendment to her trust divides the estate between her 3 grandchildren; 45% to me and my brother, and 10% to my sister, and that only I could buy out my brother and sister with the money that I would be inheriting. Approximately one month later she became disappointed after finding my brother had hired a lawyer and with his twin sister and the former POA/Trustee alongside, was trying to gain control of her funds and assets, entirely against her wishes. So, she decided she no longer wanted them to have any money from her home if they were trying to get her out of her home in order to sell it while she was still alive. That’s when she decided she wanted me to have sole ownership of her home. Since she passed, the former POA/Trustee has had an attorney serve me a Notice to Vacate as well as a Notification by Trustee pursuant to probate code 16061.7 she filed, all through the attorneys my grandma originally hired to draw up the trust. Since the former POA/Trustee was stirring up a variety of issues with the estate and fabricating stories in attempt to hold full control over my grandmother and her Trust, she went to a different attorney for the most recent amendment and restatement. The last year or more of my grandma’s life I became dedicated, as well as my girlfriend at the time, to taking care of her 24/7 with no help from the other grandchildren or the former POA. It has been very overwhelming trying to defend against malicious attacks on top of caring for her. While she was still alive, my main concern was her well being and had the to finish out her years in as much comfort and happiness as possible. so in turn I didn’t prepare for the financial part of things to come in the future and now that time has come and I’m beside myself and need some direction on how to go about carrying out my responsibilities to the promise I made my grandma to do my best at settling her estate as she wished.