My brother has bonds that belong to me but hasn't given them to me?

When Mom died she left us a nice inheritance. It was like pulling teeth to get my brother to disburse the money to me (he was named the executor). My sister is disabled and I help take care of her. My brother never visits her or helps her. He wants nothing to do with her. My sister is an in assisted living and I am her only family member left to visit and help her. Anyway, in addition to the original Living Trust that was finally disbursed Mom told me before she died there were other bonds in a safety deposit box in my name and my sisters name. My brother is holding onto them. I have asked him to give them to me or atleast cash them and put in an account to use for things for my sister as they come up (she makes a little over $1000. a month from Soc. Sec. that barely pays her rent).....he just ignores me. How can I get him to release the bonds? I don't want to fight...I am not greedy....he has just been so difficult to deal with.