I payed taxes for an estate of which I am not the executor, how can I be reimbursed for that money?

My grandmother died in November of 2017 and my aunt, who is the executor of the will, has still not carried out the stipulations on the will. All of her belongings were to be divided equally amongst her 6 children upon her death. Her house still has yet to to be sold or put on the market. I have been living in the house my entire life with my grandmother and after she died I continued loving there without any written agreement, but a verbal agreement that I will continue living in the house with my younger brother and pay the taxes on the house and I will be reimbursed when the house is sold. I am not the executor of the will nor is my name or any of the stipulations agreed upon in that verbal agreement. My Aunt is now telling me that when the house is sold I will not be reimbursed for the money I payed for the taxes and that the $17,000 I payed for the taxes will be counted retroactively as rent. How do I ensure that I will get that tax money back?