It's easy because of when the various fry appear and how they were separated to control the population. There is a correction: Brutus is also a split generation fish, G2/3.
Right now I have Mica's babies in a tub (G4) and fry from Blackbeard AND Brutus (G4). The fry from Brutus are bigger and older. In the 125 there are the three pink (G4) fry out of Harlequin, her only surviving babies. I have named one of them Deuce, who has a red cheek circle. There are a few random leftover fry from Mongo/Blaze not named. Mongo and Bianca have (G4) wigglers right now.
Renegade Baby in Lazarus' tank is out of Blaze (G3). Speaking of the miracle fish I rarely see him...he appears to be around 4 inches or more. For those of you who don't know Lazarus survived in an unused tank for over 6 months in half an inch of water and no food. His body went into survival mode and he was only about an inch even though he's the same generation as the giants! (G2). One day I'll catch and measure him for an upddate.