Over the weekend, a new Guardians of the Galaxy Vol. 2 fan theory revealed that Star-Lord and Mantis could be siblings. However, director James Gunn recently took to social media to sort of debunk the theory, while not outright denying it either. Gunn claims that it's not as big of a deal as everybody is making it out to be, but some Marvel Cinematic Universe detectives went straight to work to find more evidence. Sure enough, there was some more to the mystery than originally thought.
Actress Jennifer Sharp, who played what James Gunn calls the same species as Mantis, posted a pretty interesting picture on social media, which has since been edited. Luckily, someone took a screenshot of the picture and caption that was originally posted after Guardians of the Galaxy Vol. 2 had been released. In the caption, Sharp says that she played "Mantis' mom," while also revealing that the scene had been cut. It seems that James Gunn cut out a scene that would have proven that Mantis and Star-Lord were siblings and that Ego was actually her father.
The idea of Star-Lord and Mantis being siblings might have been explored in Guardians of the Galaxy Vol. 2 early on, but James Gunn may have decided to ditch that storyline. Jennifer Sharp's Instagram post revealing that she played Mantis' mom has since been edited to take out any mention of that aspect of her part from the film, which was more than likely a request from Gunn and the MCU. The director is probably just covering his tracks to make sure MCU fans don't latch on to the idea.
While James Gunn discrediting the Mantis and Star-Lord sibling theory may have been in order to correct an abandoned idea, it also seems equally plausible that he is keeping a surprise for Guardians 3. The director, who is always pretty straightforward with his fans on social media wasn't as direct this time around and has previously mentioned that the third and final installment will be much different from the previous two, while also being more complex as well. Having Star-Lord and Mantis end up as siblings would certainly add to the complexity to the third movie. James Gunn has an awesome relationship with MCU fans, so there's no reason for him to be deceitful, unless he's protecting his art, which is completely understandable.
Will Star-Lord and Mantis be revealed as brother and sister in Guardians 3? Anything is possible, but it looks unlikely by James Gunn's comments. There is a scene where Jennifer Sharp portrayed Mantis' mom in Guardians of the Galaxy Vol. 2 that was never used and that's the real mysterious thing about this whole story. Regardless, if it really is nothing, Gunn will probably address everything soon. Until then, you can head over to Reddit and see the original, unedited social media image that was posted more than a year ago.