From what I can tell, によって 読書 the manga. Sailor Cosmos isn't really Sailor Moon's ultimate form. She's just the ultimate form of a sailor scout in general. So in all, ちび ちび isn't related to Rini または Serena.
Yes, but in the manga, ちび ちび is the disguise of Sailor Moon's ultimate form, Sailor Cosmos. So technically wouldn't that make ちび ちび be Chibi-usa's mother, if Sailor Cosmos is Sailor Moon's ultimate form?
From what I can tell, によって 読書 the manga. Sailor Cosmos isn't really Sailor Moon's ultimate form. She's just the ultimate form of a sailor scout in general. So in all, ちび ちび isn't related to Rini または Serena.