How Brangelina of them!

Sean Penn has filed papers to adopt fiancee Charlize Theron's 3-year-old son Jackson, Us Weekly reports. "Sean always knew that to truly earn a place in Charlize’s heart, connecting with Jackson was one of the most important parts," a source close to the actor dished to the mag. "Charlize says this is it. Jackson already calls Sean daddy," another source told People.

The A-list couple, who became engaged during a trip to Paris last November, are even thinking of expanding their brood! "There is still talk of adopting again and giving Jackson a brother or a sister," the source added.

No word on a wedding date yet, but nothing says commitment like blending your family!