Stanley Yelnats II is Stanley's grandfather.
Due to having lived through a great deal of the Yalnats' family curse (Born in 1917, he was 86 at the time of Holes), he had a bleak outlook on life. He referred to his grandfather as "No good dirty rotten pig-stealing (great great grandfather) Elya Yelnats".
He could be ornery when angered, even to the cops who brought Stanley Yelnats IV (Caveman) home after catching him with Clyde Livingston's stolen shoes, snatching the "Unwarranted warrant" from the cops, much to Stanley Yelnats III's chagrin.
When the cops came into his and Stanley IV's room and saw the Sweetfeet memorabilia on the walls over one of the beds, the cops asked if it was Stanley IV's bed, and Stanley II challenged them, "How do you know it's not my bed?!" / "You don't have to answer that, we have the right to remain silent!" Then female cop replied, "Oh, wouldn't that be nice?" Stanley IV, being an honest person, revealed that the bed was his.
Stanley II was present the curse was lifted and immediately afterwards, Stanley III discovered the cure for foot odor by accidentally mixing peaches (Kissin' Kate Barlow (Katherine Barlow)'s 100-year-old fermented spiced peaches (Sploosh kept Zero (Hector Zeroni) alive in the desert) and Onions (Sam's onion field on God's Thumb kept Stanley IV and Hector alive, and cured Hector's illness caused by the fermented Sploosh]].
When the discovery was made, Stanley II was jamming cheerfully at the dining table as Stanley III and Tiffany Yelnats boogied in the kitchen / lab to Stanley III's impromptu `song' of "I Don't Smell Anything!!"
When Stanley IV and Hector were brought to the Yelnats' apartment and Stanley Yelnats I's treasure was opened, the goods were split 50-50 between the Yelnats' and Hector. Stanley II asked in amazement when Stanley IV made the deal, mentioning Hector's last name, "Did you just say `Zeroni'?!". When Hector said "Sure did," Stanley II cried in happiness and kissed Hector on the head. A Yelnats caused the curse from Madame Zeroni; A Yelnats and a Zeroni lifted the curse.
Stanley II was present with Stanley I as Hector was reunited with his mother, Stanley II earing up in joy as mother and son hugged, Stanley IV laying a comforting hand on his shoulder.
In the film he is portrayed by the late Nathan Davis, who is ironically the father of the film's director Andrew Davis.