type the plural form of the word.\n\nfather-in-law

Brief Explanations:

In English grammar, compound nouns formed with hyphens usually pluralize the principal word (the head noun) rather than the modifying phrase. In the term "father-in-law," "father" is the principal noun that denotes the person, while "in-law" describes the relationship. Therefore, the plural suffix "-s" is added to "father."

Answer:

fathers-in-law