Esteban Vihaio is an 80 year old Mexican pimp based in the border city of Ciudad Acuña who, as a friend of Bill and Budd's mother, was seen by the young boys as a father figure. His prostitutes' illegitimate children are apparently recruited into an organized crime gang called the Acuña Boys, of which Esteban is the de facto leader.

When Beatrix Kiddo visits him, he tells her of Bill's whereabouts, noting that it is what Bill would have wanted Esteban to do ("How else is he ever going to see you again?"). He also notes that if he were in Bill's situation when Bill had tracked the Bride down he says he would have only mutilated her face instead of trying to kill her, his apparent discipline of choice for his prostitutes.