Is notarized affidavit mandatory to lay down your rights as nominee?

Hello my mother had some mutual funds she passed away recently and I came to know that I was the nominee. For some personal reasons I do not want to execute this nomination and would like any of my my other brothers and sisters take over this nomination and execute the nomination independently without involving me. How do I go about doing this? Can I make a notarized affidavit saying the above which my brother or sister can give to the mutual fund company and go about encashment of the mutual funds in their names?