Task: Question Generation
Input (English): Passage: Cattle rustlers Robert Hightower, Pedro "Pete" Rocafuerte, and William Kearney rob a bank in the town of Welcome, Arizona, but William is shot in the shoulder and they have to flee into the desert, pursued by a posse led by Sheriff Buck Sweet, who shoots a hole in their water bag (that they do not notice until after all the water has leaked out). They eventually lose their horses in a desert sandstorm and end up walking. Desperate for water, they head for a water hole, which has, however, been destroyed by the misguided efforts of a bumbling tenderfoot, who then chased after his livestock and did not return. 
In a covered wagon left nearby lies the man's wife (Sheriff Sweet's niece), who is about to give birth. With the help of the trio, she has a boy, whom she names Robert William Pedro after her benefactors. Before dying, she extracts a promise from them that they will take care of him. Moved, the three desperadoes try to keep their promise despite the acute lack of water.
William is certain a higher power guided them there and likens their situation to the Three Magi finding the baby Jesus in a manger. He convinces the others to head for the town of New Jerusalem, which lies across a wide expanse of desert. While crossing a salt flat, William dies; later, Pete falls and breaks his leg. He asks Robert to leave him his pistol, for "protection from coyotes." As Robert walks away, he hears a single gunshot.
Output (English): What are the last names of the people who promise to take care of the baby?