What?No examples?
Just a cursory glance at the history of modern architecture can afford you plenty of clues-see how Le Corbusier and Frank L Wright disparaged each other's masterpieces?The striking similarities between the Prairie style and Corbusier's works in the Alps illustrated perfectly how like-minded masters downplayed one another's talents.
Also rushed to mind was the initial cameraderie and the ensuing rivalry and contention between Pablo Picasso and Georges Braque.
Then,what about the eventual split-up of the Beetles?John Lennon and Paul McCartney were once so startled by the extraordinary resemblance in their musical propensities...