After the recent rumors that new couple Sean Penn and Charlize Theron got engaged over the past month, things are getting more and more serious for the Oscar-winning pair: Penn has now officially filed to adopt Theron's son Jackson, who the actress adopted by herself back in 2012.

Although Sean Penn and Charlize Theron only became a couple recently, the two Oscar-winning performers have known each other for almost two decades, being close friends through the good and bad - including Penn's marriage to "House of Cards" actress Robin Wright and Theron's longtime relationship with actor Stuart Townsend, which lasted for about a decade.

According to Hollywood Life, the latest news from Sean Penn and Charlize Theron is that the couple is taking a step further in their relationship, working things out the way famous couple Brad Pitt and Angelina Jolie have done in the past: Penn's adopting Charlize's three year-old son, the way Pitt adopted Jolie's two children when they first got together in 2005.

As The Daily Mail reports, Sean Penn and Charlize Theron have decided to have a bigger family for the both of them, as it doesn't stop with Penn adopting little Jackson: it seems the couple also wants to expand later on and have more children, though it is unclear whether they plan to adopt, have biological children or both options.

Most of the further reports say that Penn and Theron might be planning to adopt later on, to give Jackson a baby brother or sister in the near future.

"Sean always knew that to truly earn a place in Charlize's heart, connecting with Jackson was one of the most important parts," said a source close to the "Mystic River" actor to Us Weekly, as they broke the story.

This would be Penn's third child, following daughter Dylan, 23, and son Hopper, 21, both of whom he had with former wife Robin Wright, as his marriage to pop legend Madonna didn't leave any children.

While representatives for Sean Penn and Charlize Theron haven't made any comments yet, it's clear that the new couple can't wait to spend the rest of their lives together.