No, it is singular, the possessive form of it is its. The plural form of it is they or them, and the possessive form is their.To answer the question directly: there is no such word as ITS'.
The singular possessive form is heart's; the plural possessive form is hearts'.
The possessive form is subsidiary's.
The possessive form of "synopsis" is "synopsis's" or "synopsis'."
The singular possessive is Richard's; the plural possessive is Richards'.
The possessive form is battleship's.
Bicyclist's is the possessive form.
The possessive form is librarian's.
The possessive form of "he" is "his": He did his homework after dinner.
The possessive form is posse's.
The possessive form is lawyer's.
The possessive form is whistle's.