Are both these sentences grammatically correct? [duplicate]

I have recently found the following. I do know the first sentence is wrong.

(1) "I am not a fan of him."

Meaning : I am not his fan.

(2) I am not a fan of his.

Meaning : I am not one of his fans.

But this is controversial. Are they correct? Some people say YES YES YES; others say NO NO NO. Please clarify it.

Both are grammatically correct.

In (1) try substituting a proper noun for 'him'. For example we might say, "I am not a fan of Tolstoy". This is surely fine, so going back to "him" (the personal pronoun in the accusative case following the preposition 'of') is surely also fine.

In (2), "of his" is an accepted construction, but not one that would occur to a learner of the language well-versed in the ordinary rules.

(1) and (2) mean slightly different things. (1) doesn't imply a relationship of fanship as strongly as (2) does. (2) hints that in some sense the fan belongs to, or is in thrall to, the man admired.