друг друга

Pronoun

 * 1) one another, each other

Usage notes

 * The first друг is always in the nominative case, while the second declines as necessary.
 * When used with a preposition, formally the preposition goes before the second друг (друг другом, “with each other, together”), but in colloquial speech the preposition often comes before the first друг (с друг другом).