Graph is correct, and I'm speaking here as someone who holds a law degree even if she's never used it once. If the lyrics would be objectively considered not to be attacking anyone, and you don't attach any specific names or other details in there that make them specific, then you're safe. You can indeed cite creative license and say the lyrics weren't motivated by any specific event.

Even if the song became wildly famous and someone took issue with it, your prime defense--which is always the one and only winning defense against slander or, in this case, libel, since the song would be written/recorded--is the truth. If you are faced with having to defend a charge of libel and have owned up to having written it about those two, who'd be the plaintiffs, and the statements you make in the song are objectively, provably true, then you're safe from that angle, too.

If you do produce and publish the song through a music label or even a Web site, whoever owns that label or site ought to have an attorney who reviews lyrics for precisely this sort of thing. It's routine CYA protection in the music business.