doubt in essay writing what other word can we use in place of his/her

I think, there is no word that we can use instead of his/her in single term. But if we want to use it in plural term, we use "their" instead of it. His - is used for a male. Her - is used for a female. Their - is used in plural term for both. For ex:- His wife is really very beautiful and smart. Her husband is not as smart as she is. Ria and Siya are good friends and their hisbands are also good friends.