What happens to a lien against a home when the lien holder dies?

In March of 2012 my husband and his father executed a Secured Term Promissory Note and security agreement in which Father gave son 10,000 and son gave father a security interest in a property in Barrow County, GA. The loan was due or payable in March of 2015. At that time Father had cancer and verbally stated he forgave the loan, but did not execute paperwork before he passed in April of 2015. Father was living in North Carolina and passed without a will. His wife then passed without a will. Father had three sons by a previous marriage and wife had three daughters by a previous marriage. 1- Does this type of promissory note/lien ever expire? 2- If it does not expire who owns the note? Can the note be removed if all parties sign? 3- Is it possible to sell the house without removing the note, and place the $10000 in escrow pending the outcome of a probate court judgment? or does the note have to be removed prior to sale?