There are two reciprocal pronouns: 'each other' and 'one another.' To be grammatically pure, use 'each other' with two things but 'one another' with more than two things. For the possessive, write each other's and one another's.

A reciprocal pronoun is used when two or more people, groups, or things are performing the same action toward each other. In English, we only have two reciprocal pronouns: each other and one another. These pronouns reflect that there is a mutual relationship between the subjects of the sentence.