triumvirate
(in ancient Rome) a group of three men holding power, in particular ( the First Triumvirate ) the unofficial coalition of Julius Caesar, Pompey, and Crassus in 60 BC and ( the Second Triumvirate ) a coalition formed by Antony, Lepidus, and Octavian in 43 BC.

a group of three powerful or notable people or things existing in relation to each other.
"a triumvirate of three former executive vice presidents"
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