Little Big League is a 1994 film about an 11-year-old (later turns 12) who suddenly becomes the owner and then manager of the Minnesota Twins baseball team.
Little Big League youtube video, paint scene

The start of the film explains about the life of Billy Heywood (Luke Edwards), a preteen son to a widowed single mom, Jenny (Ashley Crow). He and his two friends, Chuck and Joey, play on the same Little League Baseball team. Billy's grandfather is Thomas Heywood (Jason Robards, Jr.), owner of the Minnesota Twins. They are a last-place team (the real-life Twins finished second in the American League West in 1992 and were World Series champs in 1991, but finished poorly and began an eight-year slump in the spring of 1993), but Billy and his grandfather absolutely love each other, the Twins, and the game of baseball. When Thomas dies, it is revealed that he wanted Billy to inherit the franchise and specified that if Billy was still a minor, Thomas' aides would help him along until Billy was old enough to run the team himself.
L ittle B ig L eague