An image of an unwitting Shriver smiling alongside Schwarzenegger and two of their children at the 1998 baptism of the child the former California governor fathered with the family's housekeeper, Mildred Baena, was posted Thursday on the gossip website.
A series of photographs also showed the 63-year-old "True Lies" star sharing tender father-son moments with the child as he grew up, including teaching the boy how to play golf and swinging him playfully above his head.
In one shot, Schwarzenegger is even seen hugging Rogelio Baena -- the man who brought up the child for 13 years as his own.
Schwarzenegger and Shriver have four children of their own -- Katherine, 21, Christina, 19, Patrick, 17, and 13-year-old Christopher, who was born just five days before his half brother.
The couple announced the end of their 25-year marriage earlier this month, and Shriver, 55, could file for divorce by the end of the week, according to reports.