In 2011, the former governor of California revealed to his wife Maria Shriver that he fathered a child with their housekeeper Mildred Particia Baena.
Their son, Joseph Baena, who was 14 at the time, hadn't known about his father until the resemblance became undeniable.
Maria and Arnold have four children together, and ended up filing for divorce after 25 years of marriage.
Katherine Schwarzenegger is the first child of the estranged couple and an author. Born in December 1989, she writes books tackling self confidence and self-image issues in young women.
Two years later, Christina Schwarzenegger was born in July 1991. She is currently enrolled in Georgetown University.
Patrick Schwarzenegger was born in September 1993 and is already following in his father's footsteps. He curretly has his own clothing line that his parents helped him start when he was 15. He's also a model and testing the waters of a potential acting career.
The youngest of his children, Christopher Schwarzenegger was born in September 1997, only 5 days before his half brother Joseph Baena.
The former Terminator star has spent the last years repairing the relationships with his children, Joseph included. The 70-year-old actor admits that they all now have a "healthy relationship".
While you can see the family resemblance with his four kids, it's nothing like Joseph.