he/she, he or she, his/her, his or her – Avoid the perception that your writing is gender-biased, but never use "he or she" or "his or her" except in quoted matter. Writing in third-person plural avoids the need to use gender-specific pronouns or the temptation to mix plural pronouns with single antecedents.
In most cases, a plural pronoun should agree in number with the antecedent. For example, “The children love the books their uncle gave them.” They/them/their is acceptable in limited cases as a singular and/or gender-neutral pronoun, when alternative wording is overly awkward or clumsy.
In content about people who identify as neither male nor female or ask not to be referred to as he/she/him/her, use the person’s name in place of a pronoun, or otherwise reword the sentence, whenever possible. If they/them/their use is essential, explain in the text that the person prefers a gender-neutral pronoun. Be sure that the phrasing does not imply more than one person.