Apparently one of the things the Rock is cooking is controversy about whether or not he's his own twin brother. That's at least in the mind of "Becky," a person who now believes that Dwayne Johnson and the Rock are two different people.
A lot of people have shared this text chain, which could easily be fabricated, but the earliest version we can find after exhaustive search (five minutes of Googling) is here.
So let's play this out a little bit. You'll find that it isn't wholly bizarre. In Christopher Nolan's criminally underrated The Prestige, Christian Bale plays a magician who disguises his identical twin so that they can perform a seemingly impossible magic trick. Hugh Jackman's rival magician enlists David Bowie's Nicola Tesla to create a cloning device, which he uses to drown clones and frame Bale's magician for murder. It's a good movie.
So what does this have to do with the Rock and Dwayne Johnson. Well, what if they are different people? The Rock's signature line, "Can you smell what the Rock is cooking?" indicates casual dissociation from self. Maybe he, Dwayne Johnson, was telling the world that he was living with his twin brother the Rock. And maybe the Rock was always cooking.
The two-Rock theory has wide-ranging implications. Such an arrangement, involving a parallel Rock, would explain his constant good cheer and energy. If one half of you was free to couch potato while an identical double attended parties and smiled for you, you could rest up for your own party attendance. Dwayne Johnson is a charming guy. Maybe that's because there are two of him.
We're not ruling literally anything out. We are, after all, living in a simulation.