The Brothers Gibb had an amazing career singing together as The Bee Gees (both)

Each Brother also wrote and produced singles by themselves.
Robin Gibb - Saved By The Bell June 1969
[media=https://youtu.be/6Qahm4RKrSY]
Maurice Gibb - Railroad April 1970
[media=https://youtu.be/FZN7j1re62s]
Barry Gibb - I'll Kiss Your Memory May 1970
[media=https://youtu.be/d07fH-wl6dM]