As executor of my mothers estate I need to be able to sell the remainder of her estate - two burial plots in memorial gardens in muscle shoals.

Memorial gardens sails i muss have all 3 of my siblings to sign the deed over or get a” letter of intent from court or something” - not sure what that is - as executor i though I could sell on my on. Problem is 1 of my siblings no one knows where he is and if we fibd him he will not talk to us. The two plots are worth between $4500 to $5000 - need to know is there a legal procedure to get legal right for me to sale and what is the cost- if it is much more than around $ 500- $700 I will let it go and do nothing more on the matter