Twins came out in 1988, Schwarzenegger's first venture into straight comedy, and co-starred himself and Danny DeVito as long-lost twin brothers who could not be more different.
While the sequel has been in the works for years now, Screen Rant reports that Schwarzenegger has revealed that Murphy is officially signed on and will be the third brother.
Schwarzenegger also says the Triplets script is completed and that the plot of the film will explain Murphy's introduction by way of a “funny thing that happens in the mixing of the sperm.”
In addition to the Triplets news, the former "Governator" recently revealed the filming start date for the sixth installment of the Terminator franchise.
While speaking to The Arnold Fans.com, Schwarzenegger divulged that Terminator 6 will start shooting in summer 2018.
"We are starting to shoot Terminator 6 in June to the middle of October, so I am in that,” he said. "I am looking forward to coming back as the T-800 model. It's gonna be great with Tim Miller as the director and Jim Cameron is kind of supervising the whole thing.”
It was also announced that Schwarzenegger will begin filming Kung Fury: The Movie (a feature-film version of the short by the same name) almost as soon as he finishes shooting the new Terminator.
There are several other projects in the pipeline for as well, with him also telling the outlet, "Then we are finishing off the script now on Triplets, which is sequel to Twins. Then they are also writing King Conan. Then we just made a deal to do a series of westerns on television, so we are looking forward to that."
One thing Schwarzenegger interestingly did not mention was Expendables 4, but Randy Couture, a co-star of the franchise, did.
"I’m excited about Expendables 4," Couture said. "Right now, we’re scheduled to start filming in August and hopefully we’re able to stay on schedule. It sounds like we’re coming back to Bulgaria, which is exciting. I’ve spend a lot of time in Sofia and Varna and I’m excited to come back. I love the people (there), I love the food and I’m excited to come back."
Schwarzenegger not specifically mentioning Expendables 4 could be nothing, or it could be that he does not have a featured role this time around.
Considering that Couture says it begins filming in August if 2018, which is right after Schwarzenegger says he will begin filming on Terminator 6, one could deduce that Schwarzenegger may have scheduling conflict.
However, he only had a cameo in the first film, and a smaller role in the second, so it stands to reason that he may be able to find some time to at least shoot another cameo or a bit-part role.