One of my ancestors wrote his original will approximately fifteen years before he died. As time went on instead of writing a new will, he executed various codicils to his original will. These codicils changed specific clauses of his will. In reading these codicils, one realized that one was in reaction to his son-in-law's financial problems, one was in reaction to his son-in-law's death, one was in reaction to his daughter's death, and one was after his sons had traded farms.
If your ancestor's will had one or more codicils ask yourself what might have prompted the change?