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general::
Phrase(s): If two ride on a horse, one must ride behind.
Prov. When two people do something together, one of them will be the leader and the other will have to be subordinate. • Jane: How come every time we get together, we always do what you want to do, and never do what I want to do? Ellen: Well, dear, if two ride on a horse, one must ride behind.
McGrawhill's American Idioms And Phrasal Verbs