How could a Roman man be expected to keep track of all his bastards? Especially a military man? No doubt the landscape was littered with butter prints of Pompey.

Only when a bastard makes a name for himself (or herself) do we hear of them in history. (Cesare Borgia springs to mind. How many nameless papal "nephews" existed but remained unnoted by historians?)

I'm not saying that Quintus existed... I'm saying he MIGHT have existed but was considered non-noteworthy. There is no way to know at this remove how many bastards Pompey got because its not the sort of thing Plutarch, Livy or Suetonius or any of that ilk would have recorded. (Well Suetonius might have... gossip lover that he was.)

I'm sure some Roman males recognized their bastards as theirs, and raised them or caused them to be raised and educated. Some men were no doubt fond of their concubines.

So... why not posit that Pompey had a favored concubine at some point, and recognized her son as his... and used him in the same fashion many men have used their illegitmate sons? It seems like a good plot point to me. And that way, there are no messy ends to tie up or people arguing "but Sextus NEVER did... whatever."