better to leave two people together than for a third person to interfere My friend wanted to come along on the date between me and my girlfriend but I told him that two's company and three's a crowd so he stayed home.
TWO'S COMPANY (THREE'S A CROWD)
Meaning of TWO'S COMPANY (THREE'S A CROWD) in English
English idioms vocab. Словарь английских идиом и выражений. 2012