My father is a vietnam vetrean and as long as any one can remember is request was to be buried in a military wall with a spot next to his brother I took care of my father with no help from sibling and they cremated him and my sister kept his ashes this is not about who has his ashes its about his finall wishes please help me I me and my children do not even see his urn she will not allow it I can get names and number of people who have known my fatehr all his life and know where he wanted to laid to rest he earned that honer plese why shold one out of five kids get his asshes and his daughter who cared for him 24 7 and his granchildresn who watched him die not have a place to go visit

Who paid for the cremation? Who arranged the cremation?

Was there a Will? Were there "after death" WRITTEN instructions?

This is almost impossible to solve legally. Usually the executor gets the ashes, but not necessarily, depending on who was in contact with the funeral home. And if no one had the funds for burial (cremation is cheaper) then there wasn't much you could do there either. If you were at his side 24/7, why did all the arrangements get done by her?
Siblings often divide the ashes. Did you ask for some?
To my mind pictures and memories are infinitely more valuable than ashes, which are mostly the box they have to use in the cremation (at least in my state it's required). Be glad you were there with him in his last years, and treasure it. Have the kids take little objects to his brother's grave to leave, and make a little plaque to put next to the stone. The VA provides them for free for vets. Or make a little shrine in your yard.
You could try suing your sister in small claims court for a portion.

Your father needed not to tell a lot of people, but to write it in his will with exact instructions for the executor.

At this death, his wishes that are not written in the will, have no binding effect. The executor will follow those wishes. You will have to file in probate ( if it is still open) to have his ashes done in this manner, you will need to prove to the judge the legal right for it.

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You could try suing your sister in small claims court for a portion.

I've said it before and probably will many times again: small claims courts usually can only enter money judgments; not relplevin orders.

Many states do allow replevin in small claims, some for a higher fee.

(The TV show judges award it often - roommates with belongings, exes with cars, any movable property.)