The reveal that Radiance never even slept with Gray makes the whole forced mystery over Yomi's parentage profoundly stupid.
I could see there being a mystery* if Gray was actually banging both foxes and then left for a year, but he'd never even touched Radiance? Then there wasn't any mystery at all, it was just Fox and Gray being cruel to their daughter for the hell of it.
*My impression is that Fox's inferiority complex towards Radiance was so great that she feared Gray would reject their child if he knew Fox was the mother? But of course he never banged Radiance, so he always knew the mother had to be Fox, but played along to humor her? And if Fox had that little actual faith in Gray, then that makes her decision to abandon Yomi and chase Gray to whatever Hell he landed in even more insane than it already was.