The Mormon Osmond Brothers had a Jackson 5 sound-alike #1 hit with "One Bad Apple" released when Donny was 12 going on 13 in late 1970. (An older Osmond, Merrill, does the lead singing, but little Donny's soprano kicks it into overdrive.) Osmond said Michael Jackson later told him that the Jackson 5 had been offered "One Bad Apple" first, but chose to record "ABC" instead. (Neither song has as exciting a chord progression as the Jackson 5's first hit "I Want You Back," but, then, what song does? Now that I think about it, I'm not sure that the Jacksons' version of that song by Berry Gordy and other Motown insiders does full justice to the potential of the material. British pub-rockers Graham Parker and the Rumour used a rather different arrangement of "I Want You Back" as their concert closer, and somebody might do well right now with their own cover.)
At age 18, Donny had a hit Sonny & Cher-type TV series with his sister Marie, which, when you think about it, is pretty weird in a sort of William and Dorothy Wordsworth kind of way.
Osmond always got a lot of grief for not being quite as talented as Michael Jackson, but, then, who was?
In retrospect, you have to give Donny Osmond a lot of credit for staying reasonably sane all these years.