But, as many have pointed out, gender equality for all unknown persons is masculine, sexist and imprecise. For this reason, Merriam-Webster, the Oxford English Dictionary and the American Heritage Dictionary have recently added notes that support the use of the singular for a person whose gender you do not know. “Despite the apparent grammatical differences between a single precursor such as someone and the plural pronoun, construction is so widespread, both in print and in language, that it often goes unnoticed,” says its usual opinion on the subject. Accepting the singular gives more structural freedom, so that authors can use basic structures, difficult to avoid, such as active verbs and third-party poses with generic subtantes. Always renaming the phrase to avoid it can become a handicap. In the non-sexist writing manual, Casey Miller and Kate Swift accept or recommend individual uses in cases where there is an element of semantic plurality expressed by a word such as “everyone” or to which an indeterminate person refers, citing examples of such use in formal language.  You also propose to rewrite sentences to use a plural, eliminate pronouns or rephrase phrases to use “one” or (for babies) “es.”  The use of singulars is called “particularly frequent,” even as a “stylistically neutral” with precursors like everyone else, person or person, but more limited when referring to common nouns as precursors, as recommended in The Australian Federation Style Guide for Use in Preparation of Book Manuscripts that “gender neutral language be used” , explaining that the use of them and their singular pronouns is acceptable.  In the 14th edition (1993) of the Chicago Manual of Style, the University of Chicago Press specifically recommended that the singular use and theirs, noting a “resuscitation” of this use and citing “its venerable use by authors such as Addison, Austen, Chesterfield, Fielding, Ruskin, Scott and Shakespeare.”  This change was made from the 15th edition (2003). In chapter 5 of the 16th edition (2010), now written by Bryan A. Garner, are worded recommendations: Read more about the plural forms for the singular “them” of the people of Merriam-Webster. Most dictionaries and grammars deal with the singular use of “them” and its other grammatical forms (“their,” “them,” “them,” “them” or “theirs”). This use is also reflected in the legislative practices of other jurisdictions.
The use of generic sub-tants and generic male pronouns in written and spoken language has decreased since the 1970s.  In a corpus of spontaneous language collected in Australia in the 1990s, they had become the most widely used (and non-generic) generic pronoun.  Similarly, a 2002 study examined a body of American and British newspapers showed a preference for them to be used as a single pronoun.  Of all areas of controversial English grammar, its use to refer to a singular precursor is one of the most prominent. So the answer is the one you`ve probably reached all the time after. You don`t have to rethink things and force yourself to say they are happy.