Plural Nouns
Most nouns form their plurals by adding s or es to the singular. These plurals form their possessive by adding the apostrophe; as, horses’, countesses’, foxes’, churches’, princes’. Nouns whose plurals are formed otherwise than by adding s or es, form their possessive case by adding the apostrophe and s, just as nouns in the singular do; as, men’s, women’s, children’s, seraphim’s.
Pronouns
Sometimes the mistake is made of using the apostrophe with the possessive personal pronouns; as, her’s, our’s, it’s. The personal and relative pronouns do not require the apostrophe, but the indefinite pronouns one and other form their possessives in the same manner as nouns; as, “each other’s eyes,” “a hundred others’ woes.”
Double Possessives
“John and Mary’s sled,” means one sled belonging jointly to John and Mary. “John’s and Mary’s sleds” means that one sled belongs to John, the other to Mary.
“Men, women, and children’s shoes for sale here.” When several possessives connected by and refer to the same noun, the sign of the possessive is applied to the last one only.
When a disjunctive word or words are used, the sign must be annexed to each word; as, “These are Charles’s or James’s books.”
Possessive of Nouns in Apposition
When two nouns are in apposition, or constitute a title, the possessive sign is affixed to the last, as “For David my servant’s sake,” “Give me here John the Baptist’s head in a charger,” “The Prince of Wales’s yacht,” “Frederick the Great’s kindness.”