How can I get my brother to acknowledge me as a co-executor of our mothers will?

I am listed on my mother's will as a potential co-executor if one of my two brother's bows out of the task. One of my brothers is doing just that, but neither one of them will acknowledge that I am to take on the role. They would prefer the one brother do everything himself. Also, since Mom's death, my siblings have taken considerable advantage of me. I was told I had to surrender copies of the keys to the family house (where my daughter and I still live) and that I had to front the money for Mom's funeral (which everyone swears they will repay), as well as numerous falsehoods they are telling people, even the lawyer who had Mom's will (whom they feel is ripping them off by asking for a $5000 probate fee). I don't want to lay claim to anything. The house is over 50 years old and falling apart. I just want to have the truth on my side so I will no longer be taken advantage of. If I am acknowledged as a co-executor, will this hinder my brother's infringement on my personal life, etc? Any advice you can offer would be gratefully appreciated. Thank you in advance!