Jesus Mandam gets mentioned a few times in “Nuclear Dragons” and probably will again in “Helios on the Moon“. His supposed twin Barsine appears in both “Goddess Gambit” and “Cataclysm Catalyst“, albeit not so much so by daddy-given-name.
So does her son Thartarre Holgatson, which should give you a hint as to who she appears as. Hint 2: Who she appears as was around in “Feeling Theocidal“, which is set in (4)376 AD, but Barsine wasn’t born until December 25, 1920.
Jesse and aka Bar-Stool (or Bat-Bait, in the pH-Webworld serials of a decade past now) didn’t look at all alike. The explanation in the Web Wheaties (serials = cereals, not surreal) is that, as soon as they were born, Witches of Weir deliberately mixed up girls procreated during the Simultaneous Summonings of 19/5920.
But could they have actually come out of the same womb? Apparently it is possible, though not very likely: See super-fecundation and/or hetero-paternal fecundation here: http://en.wikipedia.org/wiki/Superfecundation.
Oh, and guess who was often called Fecundity in “Feeling Theocidal“?