A proper name in a gerund phrase

To me she looks American. Strangely enough, that corresponds to Gib Melson's being American himself.I'm in doubt in regard to the use of the genitive in the last phrase. Were it a pronoun, it would be possible to use both objective and genitive forms: his being American (formal), him being American (colloquial), right? But I'm not sure whether the following is acceptable: "... to Gib Melson being American himself." Which is correct?...Read more