That is what I have just said.
The original Ralis was actually a female Zora named Ruto.
For some reason during development, they changed Ralis into a male.
Also, the name Ralis a mistranslation of Ruto during the transition from Japanese to English, they liked the name-and kept it.
Well originally, Prince Ralis was supposed to be a girl.
They changed it afterward during developtment, but if it stayed-the Princess' name would be Ruto due to a mis translation earlier.
You could see how Prince Ralis could be Ruto.