Analysis of information sources in references of the Wikipedia article "Singular they" in English language version.
Like singular you, singular they is treated as a grammatical plural and takes a plural verb.
Use themselves as the reflexive/intensive pronoun to refer to an indefinite gender-neutral noun or pronoun that is the subject of the sentence and avoid themself.
...the most natural-sounding verb is the one to use. 'They' always goes with a plural verb...
... our pronoun they was originally borrowed into English from the Scandinavian language family ... and since then has been doing useful service in English as the morphosyntactically plural but singular-antecedent-permitting gender-neutral pronoun known to linguists as singular they.
Like singular you, singular they is treated as a grammatical plural and takes a plural verb.
...the most natural-sounding verb is the one to use. 'They' always goes with a plural verb...
... our pronoun they was originally borrowed into English from the Scandinavian language family ... and since then has been doing useful service in English as the morphosyntactically plural but singular-antecedent-permitting gender-neutral pronoun known to linguists as singular they.
Use themselves as the reflexive/intensive pronoun to refer to an indefinite gender-neutral noun or pronoun that is the subject of the sentence and avoid themself.