Two's company, three's a crowd

Generated image of a dog intruding on a couple's personal space
Two's company, three's a crowd means that two people often enjoy privacy together, while a third person can interrupt that closeness. The phrase is often used when a pair would rather be alone.

The saying appeared in English in the 1600s. It reflects the long-standing idea that couples prefer time without others around.

When their friend tried to join them at the quiet table, he laughed and said two's company, three's a crowd.