Do I have any recourse to get it back to the rightful side of the family?

My Grandmother told my mother and I that she had given her other daughter other heirlooms and that my mother was to pass it down to me to pass to my children. My mother gave the dipper to her sister as a gift against my grandmother’s wishes and hid the fact from me for many years as my mother is now in passion of her things. I would like the dipper back and had asked her to ask for it back but she refused because she did not want to hurt her sister’s son that now has it. He refuses to give it back to the side of the family. Our grandmother wanted and trusted her daughter to pass it down. This item was treasured by me and it was well known that it was to come to me and even promised to me by my mother. My children were also told it would be theirs. I have to say my mother suffered brain damage prior to her giving it away and has never been the same. I want what was intended to be passed and promised to me since it was to come to me by my grandmother. My cousins’ comment is he has it and at least it’s still in the family. He never would have known about it if my mother had honored her mother’s wishes. This heirloom has always been passed to a female member that carries the family name as my mother carried the name as I was given the name and my daughter was given the name. I was also my grandmother’s only granddaughter. Also this cousin does not know the history of this dipper as I was told it by my grandmother who did not even tell the history to my mother just that it had belonged to her family. This heirloom survived the civil war and dates back to the 1830's. Also my cousin side of the family already had the family letters from and another family dipper that our grandmother had given them. I live in NC, mom lives in SC and cousin lives in AZ.