A comment made in one of the older Japanese Final Fantasy guidebooks sparked a long-running debate regarding a connection between Final Fantasy VII and Final Fantasy X, and it seems that Final Fantasy VII Remake has added fuel to the fire with a hidden reference to Shinra from Final Fantasy X-2.
In the Final Fantasy X-2 Ultimania Guide Book, Kazushige Nojima (scenario writer of Final Fantasy VII, X, and X-2) made an off-hand remark about how Shinra (the young scientist from Final Fantasy X-2) would go on to become the founder of the Shinra Corporation in Final Fantasy VII. This was supported in Final Fantasy X-2 by Shinra talking about how he'd like to harness the power of the Farplane and use it as an energy source, but it would take generations of research to accomplish. The creators of both Final Fantasy VII and Final Fantasy X/X-2 have toyed with the theory in interviews in the past, but it doesn't seem to be something that is intended to be set in stone or taken seriously.
It seems that the creative minds at Square Enix love to keep fueling the fires of fan theorists around the globe, as there is a hidden reference to Final Fantasy X-2 in Final Fantasy VII Remake. According to the AllGamesDelata Twitter page, there is an old photo within the Shinra Headquarters showing a group of employees. Sitting at the front of the crowd is a person wearing a mask that greatly resembles the one worn by Shinra throughout Final Fantasy X-2.
This photo is likely just an easter egg added in by the developers, due to all of the discussion that has been made over the theory. It's unlikely that future entries in the Final Fantasy VII Remake series will heavily reference the theory or make a plot point out of the connection. Don't expect for Avalanche to wake Tidus up from cryosleep and have a good laugh with him outside of Junon.
The Final Fantasy games have usually only been connected in Easter egg-style references or through multiverse shenanigans, such as with the Dissidia games. The idea of Final Fantasy VII and Final Fantasy X/X-2 existing in the same world is sacrilege to some fans, but it seems that the developers of both games love to throw in references, just to tease the most dedicated of theorists.
Final Fantasy VII Remake is available now for PlayStation 4.
Source: Twitter