Caine's niece

I don't know but I would have liked to see Horatio's family explored more.

Based on how the episode ends, I would think that we're supposed to believe that Ray Jr. was a match and made his donation and Madison was cured, that Horatio continued to pay the bills for the hospital and contribute to Madison's general care, and that the whole Suzie situation never really caused Horatio any problems ever again.

I have a far bigger issue with the fact that dark-haired Ray Jr. (whose mother is Colombian) is a better match red-haired Madison (whose mother is blonde and pale) than her red-haired uncle (whose mother and father are Madison's grandparents). Yes, it's true that relatives are generally better matches than non-relatives. It's also true that there is a theoretical potential for two brothers to have virtually no genes in common except the Y chromosome, but that same fact makes it all the less likely for half-siblings of different sexes to be a match, especially where one's mother is Irish (or at least Northwestern European) and the other's mother is Colombian (like it or not, race matters when it comes to bone marrow matching).