The one with red hair is called Little Rabbit (most people call it Little), which is also a cartoon version of the future beautiful girl warrior, that is, Sailor Cosmos. The animated version is the seed of Galaxia stars and the light of hope.

The one with pink hair is called a beautiful girl warrior (because there is a beautiful girl warrior, everyone calls him Chibiusa).

It's the daughter of bunny and tuxedo mask.

So the rabbit has no sister. But there is a brother on the earth.