Ryouga is an only child. In the story where Ryouga's dog Shirokiro
(horribly translated by Viz as Checkers!! in the most recent issue) has
puppies, he is amazed that he has a sister (Ranma dressed up as a Hibiki)
because he doesn't have any family besides his parents.

Unless something happened while Ryouga was lost, or his Mom and Dad were
lost...

etc.

misachan

On Mon, 14 Oct 1996 rsalva1@UMBC2.UMBC.EDU wrote:

On Mon, 14 Oct 1996, Philip Mak wrote:

Correct me if I'm wrong, but I didn't know Ryouga had a sister?

I believe it was never discussed in the manga series.  Maybe he had 8 
brothers and sisters with fangs and headbands. 

-Ramon