theirselves

pronoun

1. The reflexive case of they, the third-person plural personal pronoun. The group of people, animals or objects previously mentioned, as the object of a verb or following a preposition (also used for emphasis).“They are going to try climbing Mount Everest themselves.”
2. The reflexive case of they, the third-person singular personal pronoun. The single person previously mentioned, as the object of a verb or following a preposition (also used for emphasis).“Everyone must do it themselves.”