Sean Penn to adopt fiancee Charlize Theron's son

Actor Sean Penn has filed for adoption papers to make fiancee Charlize Theron's 3-year-old son Jackson his own.

According to a close pal of the star, 54, Penn wanted to truly earn a place in Theron's heart, and the actress is really delighted with his act, Us Magazine reported.

The couple who got engaged after dating for over a year, haven't set a wedding yet, but reportedly plan to have more kids in future. Penn, who was previously married to Madonna and Robin Wright, already has a daughter Dylan, 23, and son Hopper, 21.