The other child-level branches - GHI and MNO - all split into three at once, but the "Snicket" branch appears to split into two before the JK branch then splits again. It's as if they were born as one and then became two. It's the sort of thing you can easily miss, but it looks very deliberate when you take it in conjunction with one of the ASoUE calendars, which marked Jacques and Kit's birthdates on the same day.
It's implied at one point that Gregor was very old, which I think makes it unlikely that Hector was his brother - though it may have been one of the spaced-out families that are apparently common in VFD. (As for Josephine's age, that is now an insoluble problem, given that she's an old woman in TWW but a girl in SYBIS.)
'The difference between the two sides of the schism is that one side puts out fires, and the other starts them' - Klaus Baudelaire.
Interesting how distinctive the J and K branches are from the others. Personally, I can't help thinking that makes the twin belief more cannonical than theoretical. I've always seen Josephine as prematurely gray, and unless I'm blanking on some other distinctive features, I'm not sure there is a disparity between TWW and SYBIS. We can't pinpoint her age, but it's not implausible that she's older than Lemony (Kit or Cleo's age, maybe); her timid nature in TWW combined with the gray hair would be enough to misconstrue her as old. Olaf is the only character that repeatedly calls her old--Lemony never does--and it's hard to say how seriously we can take his statement. Whether it's accurate or not, it's a good insult, and petty enough for him, again regardless of fact.