everyone and their brother

Pronoun

idiomatic

(idiomatic) A large number of people; most people.

Japanese Meaning

大勢の人、ほとんどの人（多くの人を指す口語表現）

When the new café opened downtown, everyone and their brother lined up for the free coffee.

新しくダウンタウンにオープンしたカフェには、無料のコーヒー目当てで大勢の人たちが並んだ。

Sense（1）

(idiomatic) A large number of people; most people.