Meet Arnold Schwarzenegger’s 18-Year-Old Son Joseph Baena .

Joseph is looking so grown up!

Schwarzenegger fathered his son with his former housekeeper, Mildred Baena. The action star has four additional children with ex-wife, Maria Shriver – 26-year-old Katherine, 24-year-old Christina, 22-year-old Patrick, and 18-year-old Christopher.