So "Yahya" is a name and "Yafya" isn't?
Bullshit. Anything can be a name if you want it to be.
I once named a kitten Hamstring on a whim. The mother was named Argenta, also named by me. Technically Argenta was my little sister's cat, so I suppose she was responsible for Hamstring too... but my sister was rubbish at names. She wanted everything to have really boring, traditional names like "Mary" or "Alice". She didn't mind too much when I named Argenta (because the cat was silver)... but when I named Hamstring, my sis threw such a tantrum.
Best thing was that Hamstring remained Hamstring because I named her first and by the time my sis came up with a boring name for the kitten, everyone was already calling it Hamstring.
So yeah. The horse can totally be Yafya or Yahya. It doesn't matter. They both sound fuckin stupid to me. The horse is a total bellend anyway.