Judgement of Possession in a Louisiana Succession for Real Property in Mississippi...?

My mother and father were divorced in Feb.1966. My father went into a deed for land contract in Nov.1966 for property in Mississippi. In Nov.1968 my father ped away, leaving my mother a letter he wrote(which I found in the trash) in Jan.1968 telling her that if anything happens to him he wants me, his only child to get his land he was buying over in Mississippi, he told her to finish paying it off, with money that she would get from his retirment and S.S. and let me know it came from him... Succession was opened in Jan.1969 which placed me as the sole heir on the Judgment of Possession. My mother some how got title to that property in her name and in 1999 she put the property in my half brothers name...When I tryed to talk to them about it, they got ugly and defensive. They told me it was their land. They left me no chose but to get an attorney, now im having to sue them...My question is...Am I wrong for sueing my mother and her son for what my father wanted me to have?