They are the grandson and grandaughter of one of B.J's daughters Soph or Jess (who used to call themselves nicknames of Arthur and Kenneth based on a series of adventure stories starring those characters names).
Behind the scenes[edit | edit source]
They are the third generation to be named Billy Blazkovitch (second generation to use the shortened version Blaze). I.E. Billy and Biilie Blazkovitch III.
If they are part of the original ID timeline they would be the third generation to hold the B.J. Blazkowicz name, the great grand children of William J. Blazkowicz (Classic), although the family photos seen in the trailer suggests that they are part of MachineGames timeline as the B.J.'s appearance from Wolfenstein II: The New Colossus and Jessie "Jes" and Zofia "Soph" Blazkowicz are seen on them.
The developers have stated they are children of the famous father Commander Keen from the original games during the E3 debut. Which implies they are sequels to the original games, however that doesn’t mean the original games are necessarily interpreted in the context of the original timeline (as a sequel to classic Wolfenstein). For example is their father still the son of Arthur Kenneth Blaze from the original series. It doesn't appear that Arthur Kenneth Blaze still exist having been turned into two seperate ficitional characters and split into the two daughters of MG's B.G, Blazkowicz. Family photos do not show any examples of Arthur of his wife.