It's a father-son getaway!

Arnold Schwarzenegger was joined by son Joseph Baena on a trip to Munich, Germany, to celebrate Octoberfest and to ring in the teen's 19th birthday on Sunday.

"Happy birthday, Joseph," Arnold wrote next to a photo of the duo, who donned traditional lederhosen for the festivities. "Great student, great athlete. I'm proud of you and I love you!"

MUST SEE: Click For More Handsome Celebrity Dads and Their Sexy Sons!

The pair famously reunited after it was revealed in 2011 that Arnold fathered Joseph with his family's former housekeeper, Mildred Baena, which eventually led to his split from wife of 25 years, Maria Shriver.

The former governor is also father to daughters Katherine, 26, and Christina, 25, and sons Patrick, 23, and Christopher, 19.