It's not unusual for a soap character to come back from the dead as his own long-lost sibling, but it's rare to return in an unrelated role. Leigh J. McCloskey, though, has done it twice: On Santa Barbara he went from gynecologist/rapist to crusading attorney, and on General Hospital he was a surgeon before becoming Damian Smith, a nefarious, sex-obsessed businessman. ''The daytime audience doesn't have any trouble accepting it,'' says McCloskey, who also played Lucy's ex-husband on Dallas. This week he moonlights in Accidental Meeting. No stranger to TV movies, McCloskey starred in two '70s Alexander films about a male prostitute. ''I'm always surprised at how many thirtysomethings relate to those,'' this father- of-two jokes. ''I guess I was the hustler for a generation.''