B so like i don't exactly remember possessive pronouns, but from the name of them, it's like a pronouns taking possession of something. for possession a pronoun would be in the form of his,hers,or theirs. that object is (his/hers/theirs). so being used that way there is no apostrophe, the only way there would be one would be saying like they're, meaning they are, and that wouldn't be possessive. there's no way for any pronouns to have an 's and be possessive over an object.
