I considered that cursed form/normal form thing but since I can't
remember it being delt with in the manga that way I suppose it would be up
to the writter.  I just find it more interesting, by my logic a jusenkyo
cursed person would be 1/2 human 1/2 animal making their child 1/4 animal
unless of course they opt for the 1/4 human but I'd rather not get into
that.

 >so, by that logic, ranma's son has at least a 1 in 4 chance

of being gay?

 >more seriously though, i don't think they're half and half. as

an animal, they still have human thoughts and the like, and that's
gotta count for something. 

  >                      -evilme

Somehow I don't think that the curses are passed from one generation to the 
next. And even if they were, you can't have 1/4 unless you have 4 forms. If 
you wanted to make the curse weaker (because of one un cursed parent) you 
could change the water temperatures needed. Say that the cold water has to be 
COLD to change into the cursed form, and (depending on which way you feel like 
working it out) that it takes lukewarm water to change back to the original 
form. If you want an interesting effect, make the 'hot' water temperature too 
high for the cursed form to withstand, making it painful to change back.