The emperor has 108 wives, if I remember correctly. Some of the siblings are full siblings (i.e. Lelouche and Nannaly, or (I think) Euphie and Cornelia), but all the others are half-siblings (same father, different mothers) and possibly step-siblings. I think Lelouche's mother was from another country, so probably some of his wives are from conquered lands. And if Nannally is...77th or 87th in line, that means there's at least that many children.
(no subject)