Arnold Schwarzenegger’s children post throwback photos while wishing him a happy 73rd birthday 

Arnold Schwarzenegger’s son Joseph Baena shares rare childhood snap with his dad… as he joins siblings wishing the actor a happy 73rd birthday

Arnold Schwarzenegger marked his 73rd birthday on Thursday with birthday wishes from his children. 

The actor and former Governor of California’s once ‘secret son’ Jospeh Baena shared a rare snap from his childhood with his father, before his paternity become known in 2011. 

‘Wishing the happiest birthday to my dad,’ the 22-year-old wrote to Instagram. ‘You are and will always be “numero uno.”

Number one: Arnold Schwarzenegger once ‘secret son’ Jospeh Baena shared a rare snap from his childhood with his father to mark the actor’s 73rd birthday on Thursday

In the photo, a young Jospeh clings to his father, resting his head on his shoulder, as the Terminator star wraps his arms around him. 

It is a rare and sweet snap made public of Arnold and Jospeh during his son’s childhood. 

Jospeh is the son of the actor and the former Schwarzenegger housekeeper Mildred Baena. 

He was born just weeks after Arnold and Maria Shriver’s youngest son Christopher in 1997.  

'Best training partner': The revelation that Arnold fathered a son outside of his marriage to Maria made headlines in 2011 and since the father and son have built a strong relationship and often hit the gym together

‘Best training partner’: The revelation that Arnold fathered a son outside of his marriage to Maria made headlines in 2011 and since the father and son have built a strong relationship and often hit the gym together 

Celebrating: 'Happy Birthday daddy,' his eldest daughter Katherine wrote to Instagram. 'I love you and can't wait to celebrate you!' The 30-year-old author also shared a photo from her youth, as Arnold carried her on his back they both beamed big smiles

Celebrating: ‘Happy Birthday daddy,’ his eldest daughter Katherine wrote to Instagram. ‘I love you and can’t wait to celebrate you!’ The 30-year-old author also shared a photo from her youth, as Arnold carried her on his back they both beamed big smiles 

The revelation that Arnold fathered a son outside of his marriage to Maria made headlines in 2011 and since the father and son have built a strong relationship and often hit the gym together. 

Last year for the actor’s 72nd birthday, Joseph shared a picture working out in the gym while his proud ex-bodybuilder father posed beside him and smiled.

‘BIG happy birthday to the best training partner in the world! Love you dad,’ wrote Joseph in the caption, at the time, geo-tagging Gold’s Gym.

Stud: Midnight Sun actor Patrick dug up an old video of his dad from his career and wrote 'Happy birthday stud.' ' 'I can smoke stogies in my house,' Arnold says holding up a cigar in the video. 'Because my father introduced me to stogies and because I'm a stud'

Stud: Midnight Sun actor Patrick dug up an old video of his dad from his career and wrote ‘Happy birthday stud.’ ‘ ‘I can smoke stogies in my house,’ Arnold says holding up a cigar in the video. ‘Because my father introduced me to stogies and because I’m a stud’

Arnold’s other children also posted in honor of his birthday. 

‘Happy Birthday daddy,’ his eldest daughter Katherine wrote to Instagram. ‘I love you and can’t wait to celebrate you!’ 

The 30-year-old author also shared a photo from her youth, as Arnold carried her on his back they both beamed big smiles. 

Katherine is expecting her first child with husband Chris Pratt, 41. 

Dip: Christina also shared a photo from her childhood with her dad, as he dipped her close to the ground in his arms

Dip: Christina also shared a photo from her childhood with her dad, as he dipped her close to the ground in his arms 

Continuing the birthday wishes, his daughter Christina, 29, and son Patrick, 26, also posted for him. 

Christina also shared a photo from her childhood with her dad, as he dipped her close to the ground in his arms. 

She also included a more recent photo with the father-of-five as they enjoyed the snow on a trip together.  

‘Happy Birthday to the only person who can get me up for a 7am bike ride,’ Christina wrote. ‘Love you more than you know.’

Now: She also included a more recent photo with the father-of-five as they enjoyed the snow on a trip together

Now: She also included a more recent photo with the father-of-five as they enjoyed the snow on a trip together 

Early bird: 'Happy Birthday to the only person who can get me up for a 7am bike ride,' Christina wrote. 'Love you more than you know'

Early bird: ‘Happy Birthday to the only person who can get me up for a 7am bike ride,’ Christina wrote. ‘Love you more than you know’ 

Midnight Sun actor Patrick dug up an old video of his dad from his career and wrote ‘Happy birthday stud.’ 

Adding: ‘This video pretty much sums you up…and hopefully brings a lil much needed laugh to people’s day! Love you tons.’ 

‘I can smoke stogies in my house,’ Arnold says holding up a cigar in the video. ‘Because my father introduced me to stogies and because I’m a stud.’