Sean Penn Legally Adopting Charlize Theron's Son

Sean Penn and Charlize Theron (Getty Images)
Sean Penn and Charlize Theron (Getty Images)

Are wedding bells about to ring for Sean Penn and Charlize Theron? It certainly appears that way as the actor has filed papers to adopt Charlize's 3-year-old son Jackson.

It has been rumored for months that the couple — who have been dating for over a year — is secretly engaged. Athough neither Penn, 54, nor Theron, 39, have commented on the speculation, a source tells People, "This is the first step toward them getting married."

"Charlize and Sean are very serious," adds the insider. "Charlize says thisis it. Jackson already calls Sean daddy.

The Mad Max actress adopted Jackson in 2012 when he was 4 months old. Penn has two children from his marriage to Robin Wright — daughter Dylan, 23, and son Hopper, 21.

And it sounds like Charlize and Sean have plans to expand their brood. "There is still talk of adopting again and giving Jackson a brother or a sister," a source tells Us Weekly.

Although the Oscar-winning duo prefers to keep a relatively low profile, Charlize did open up about their relationship last year in Vogue.

“Look, we’re dating, and I don’t think we were trying to hide anything," she admitted. "We were photographed; the relationship was kind of written about… What I will say is, I was single for a really long time. I was enjoying mommyhood. You just naturally become kind of selfish about your time, and all of it is dedicated to this little thing, whether he needs it or not. And then they get into more of a schedule and you start to think, 'Wow, wait a second. There’s this passionate creature in me.' And going about dating in your late 30s is such a different ball game. I know so well what I want to fit in my life. And the simple answer to that is: Unless he can make my life better? My life is really pretty f--king good.”

Related: See Pics of Charlize and Sean's Romantic Ride

Theron continued, "I really didn’t see it coming. Sean and I have known each other for 18 years. We were just really good friends. And it’s been slow going because you are aware that you could screw that up and lose it. We had to think about it. But at the end of the day, it was somewhat effortless. It just kind of naturally happened, and before I knew it, I was in something that was making my life better — the people who really love me can see the effect it has had on me.”

Clearly, Jackson approves.