I've been relistening to Captain Vorpatril's Alliance and there's a line "till Gregor married Laisa Toscane and the boys came along, to many people's relief.”, so I'd guess the sons are older than the daughter. Which was obviously, as the quote indicates, a political decision as much as a personal one, presuming that uterine replicators were involved. I haven't read Flowers of Vashnoi yet either.