I’m doubtful Zeno is a child. Child-like? Sure. But when he’s the king of all and there’s literally no reference to his having a parent, whether alive or dead, that came before him, more likely than not, he existed since before even Majin Buu was born. And BTW, might as well add to this, Majin Buu was over a million years old at the very least, and he acts like a child all the time despite clearly not being that. Not to mention it’s made explicitly clear in repeated sources that Zeno literally cannot be supplanted, killed, defeated, what have you, with Shin making such VERY clear in the manga, and even the likes of Future Zamasu having dread at even the mere possibility of Future Zeno finding out about their Zero Mortal Plan and it resulting in their demise. This is absolutely NOTHING like the example from Final Fantasy V.