Modern English Grammar rules demand that instead of using “his or her” where or when pronouns like “someone, everyone, every person, anyone” are used, the plural pronouns “they, them, their” should be used to portray in place of the singular pronouns “he and she”. This is because, a particular gender wasn’t specifically referred to by the use of “someone, everyone, every person and anyone”. It’s wrong to assume it may be a he or a she, hence no gender was mentioned.
Examples:
1. “Someone” has to know “their” rights in a society replete with injustices.
Judgment: “Someone” doesn’t mean a particular gender. It’s either a he or a she, since it’s not specified, “their” should be used.
2. Every person in this house should respect “themselves” (instead of him or herself).
3. Anyone caught embarrassing “themselves” here will be punished.
4. Everyone invited for the occasion was there, so, “they” fulfilled “their” promise of attendance.
Therefore, whenever you see either myself or anyone else write or speak in the above way, don’t say, or assume that the grammar is wrong.