What is the best way to avoid a lawsuit by my siblings who are listed as 'predeceased' in my father's will?

I am the only one of four children who is willing to care for my parents. My mother was diagnosed with Lewy Body Dementia summer of 2018. She is in the early stages of this disease, so she can still make decisions, write her name, carry on conversations, etc.

I am POA and in charge of my father's 'Advance Directives'. My parents' lawyer insists on a guardianship for my mother. This is a very complicated, expensive, and time-consuming process. Then the lawyer stated to me that my mother may be quite capable of signing POA and 'Advance Directives' documents. He refuses to do this though. Whatever! It has been difficult handling my parents' affairs because they own everything jointly. I don't have rights to assist my mother with her half.

My father and I are joint owners on a savings/checking account at a different bank. The savings account is strictly to be used for purchasing a new home (condo), for their current home will have to be sold 'as is'. My significant other (Gary) and I are full-time caregivers for both of my parents. We are in the process of clearing out their home, which is a very stressful job because they were hoarders. Gary is listed as beneficiary on this separate account.

My siblings and I are listed equally as beneficiaries on my parents' life insurance policy. However, my father willed all of his property and possessions to me. He declared my siblings to be considered 'predeceased' and disinherited them in his will. My parents did list my younger sister and me as 50% beneficiary (equally) on all of their bank accounts. They both decided to add me as joint owner on their said bank accounts last fall.

I am in charge of hiring caregivers to assist Gary and me. I am also in the process of taking them to an adult daycare facility a couple days a week. We are planning to take my parents on outings when the weather is warmer. I told my parents that I want them to enjoy themselves and spend some of their money while they are living.

My siblings do not check in on my parents. They all have my phone number and address; plus they know our parents' are living with Gary and me. Phone/text messages are not returned.