So before we get to the answer I want to give my guess.

So all 4 parents/guardians are in on it. The Granddad finds and hunts the monster, and probably sends the material to Rose’s mom to duplicate it and see what it is. John’s Dad’s shave chat might just be a deception to fool people from his spy chat. And who knows what Bro does.

But this is where both sides get enough pieces to keep the war at stalemate. Or the guy who created the game make multiple copies so he can start multiple sessions of SBURB at once