"Father and son reunion. #Logan #Charles #Wolverine," Jackman said on Twitter alongside a photo of the pair enjoying a conversation at a dinner table.
Jackman's use of the phrase reflects their characters' relationship in the X-Men series, as Professor X (Stewart) mentored and cared for Wolverine (Jackman).
A scene from Logan, which was released in March, featured Jackman referring to Stewart as his father as a way to conceal their identities.
Logan was touted as Jackman's final run as Wolverine after having played the character for 17 years across seven movies, including one cameo role. "This will be my last one," he said in October 2015. "It is my last time ... It felt like it was the right time to do it ... And let's be honest, 17 years. I never thought in a million years it would last, so I'm grateful to the fans for the opportunity of playing it."
Stewart similarly said Logan would be his last film as Professor X, also known as Charles Xavier, stating that he came to the decision after viewing the film alongside Jackman.
"As I sat there I realized there will never be a better, a more perfect, a more sensitive, emotional, and beautiful way of saying au revoir to Charles Xavier than this movie. So, I told [Hugh] that same evening, 'I'm done too. It's all over,'" Stewart said.
Jackman has expressed interest, however, in remaining as the iconic mutant if it meant that Wolverine could appear in an Avengers film. "I always love the idea of him within that dynamic, with the Hulk obviously, with Iron Man but there's a lot of smarter people with MBAs who can't figure that out [laughter]. You never know," he said.