|Nunnally is Charles's 87 seccessor how many kids can you have in a 30 year period.|
Schneizel is 30, and presumably his older brother Odysseus is at least a year older. The youngest we know of is Nunaly, who is fifteen, so that's a 16 year period total. And really, the only limiting factor to how many children you can have is how many women you have available to you, and Charles supposedly has 108 wives.
(16 y / 9 m) * 108 = 2304