1. A chapparal is a shrub found in the Arizona desert.
2. Blue Boy, aka Billy Blue (Mark Slade) was the teenage son of Big John (Leif Erickson), who ran a ranch in Arizona.
Early in the series, Big John marries Victoria (Linda Crystal), daughter of the rancher next door. She arrives accompanied by her brother Manolito (Henry Darrow, right, the one with the beneath-the-belt potential).
Sounds like a testosterone-intensive ranch. I wonder if there was some buddy-bonding? From what I can tell from the very extensive episode guide, Buck and Manolito form a nice homoerotic bond, while Billy Blue is a surly teenager who digs the ladies.
Mark Slade, although almost thirty years when he played the "surly" teenager, received some teen idol attention. He got his start on Broadway, and starred in Voyage to the Bottom of the Sea and Gomer Pyle before High Chapparal. Later he left acting to become an artist.
Henry Darrow, who was born Enrique Thomas Delgado, made hundreds of movie and tv appearances, including the Hispanic hero Zorro (in the series Zorro and Son).