No, there are only 4 movies in the Ju-on (呪怨) series.
Juon 2 (2000)
Juon - The Grudge (2003)
Juon - The Grudge 2 (2003)
The two USAian movies are remakes (copies?) of the last two.
I haven't seen the American version of the Grudge, but I was under the impression that the Grudge 2 was completely different from Juon 2 (which sucked, by the way).
Or was that Ring 2 and リング2 I was thinking of?
Too many damn American Remakes.