Summer of the Colt (1991)

This award-winning film by André Melançon -- set on a ranch on the pampas of Argentina -- tells the story of three children spending a summer with their grandfather. The youngest, Felipe, makes friends with a puppy; his older brother, Daniel, breaks and train his first horse; their 13-year-old sister, Laura, struggles with the transition between childhood and growing up. The kids find it difficult to adapt to their proud and stubborn grandfather, and he learns that he has to change his ways and try to understand them as they all experience the joys and sorrows of growing up and growing old. ~ Alice Duncan, Rovi

Unfortunately the movie Summer of the Colt is not yet available on HBO Max.