That must have been one juicy cat story the girls were sharing.
Beatrix and Montague had two sets of twins which added to their family size. Most of my second generation upper class sims have four or five children, so they have a larger family than most. My most fertile couple though is Nicolette and Trevor. They have nine children together, including 3 sets of twins! Plus Trevor has an additional set of twins from an affair he had with the local witch. I try to avoid giving my sims the aspiration bonus that increases the chance for twins, but I made an exception for Trevor since both of his love interests at the time were twins themselves. I know Nicolette is too close to elderhood to have any more babies, but Beatrix might still have time to catch up if she and Montague are so inclined.