NSN.-The rapper-turned-actor says he’s “grown a lot” since writing the Grammy-winning 1988 hit that humorously declared they didn’t.

All three of his children now at least dabble in music and acting, most notably 14-year-old Jaden, who stars with his father in the new sci-fi film “After Earth,” opening today. Even in the midst of a globe-hopping promotional tour for the movie, Smith recognizes the downside to making stardom a family affair.

“I think that the major risk of this particular business is strictly emotional,” he said in a recent interview. “The business has almost a narcotic quality. So it’s almost as if you’re introducing a narcotic into your kid’s life.

“So for wife Jada Pinkett Smith and I, the most important thing is that they have to stay focused and grounded on the fact that they are giving. You don’t make movies for your ego. You make movies to transfer information, to bring joy, to add value to the world.”

When Jaden loudly drops a water bottle during a TV interview, he’s quickly reprimanded: “You’re kidding, right? You’re kidding. That’s the most unprofessional thing I’ve seen you do.”

Smith reaches over to shield his son’s face from bright camera lights, taunting the teen as a “super mega movie star, towering over you like a shadow over you. And you’re living in his shadow. And you’ve got to do interviews in his shadow.”

Jaden, obviously accustomed to the teasing, responds with calm confidence and some of dad’s hammy humor, saying he lives “naturally” in the spotlight.