The actor took to Instagram on Sept. 11 to share an image of Dimitri Portwood Kutcher wearing a "That '70s Show" shirt. The shirt depicts Mila and Ashton as their "That '70s Show" characters, Jackie and Kelso. The words "Hello Wisconsin" -- a phrase that was shouted at the end of the sitcom's title sequence -- were also on the throwback T-shirt.
"Yes, this Is my son's outfit today. #that70sshow #kelsoandjackieforever," Ashton captioned the snap, which doesn't feature his son's face.
The fact that Ashton didn't show his son's face in the Instagram post shouldn't come as a surprise, as he and his wife are fiercely protective of their children's identities.
In 2015, the high-profile couple sued Associated Newspapers, the publisher of British website MailOnline, after the Mail published photos of their daughter, Wyatt, who was 1 at the time.
Ashton and Mila argued that the images were taken during a private family outing on the beach and they accused a paparazzi photographer of using a long-lens camera to snap photos. The family was unaware they were being shot. They claimed that the photos breached the Data Protection Act and were used for the unauthorized promotion of clothing on the website, the Los Angeles Times said.
The couple settled the case last month.
On Aug. 25, legal reps for the publication and the couple issued a joint statement to The Times, saying, they "have reached a satisfactory resolution of their legal action, which includes an agreement to pixelate photographs of their daughter, Wyatt, their son, Dimitri, and any future children they should have together."