Hey Borgoff,
alot of stuff discussed feels like a "what if Skullknight is Guts from the future?!!!!" theory that the child is Griffith.
Please do me, yourself, and everybody else a favor by not making this kind of comparison. We're talking about a theory that has a lot of elements behind it and that has virtually no viable alternative here, so I'd like to see you put some more effort into proving your point if you're going to say that. We already know that Femto was incarnated in the Demon Child's body. That he felt the child's emotions inside of him. And everybody's assuming the Demon Child and the Moonlight Child are related, or even that they're one and the same. This was the missing link, although nothing is confirmed yet. If the Moonlight Child is Griffith then it allows him to be the Demon Child too, and it explains his power and a lot of other things. A lot of elements fit, that's the reason people are pumped about it. After that, if we take for a premise this theory is true, the real question is to know how exactly they interact and coexist. A lot of variants are possible that could really go from one side to the complete opposite, and I invite everybody to share their (serious) thoughts about possible scenarios. You also say that:
Obviously he is related to Griffith...literally.
Well then how exactly is he obviously and literally related to Griffith if the idea seems totally ridiculous to you (which is what the "SK is Guts from the future" joke is)? It seems somehow contradictory to me. Plus it's just a kid that showed up on the beach, maybe he's the Hanafubuku Ô.
although you raise fairly valid points, I'm gonna have to see to believe on this one.
Sure, it's up to you.

We will probably have to wait at least till the next full moon for futher evidence.
Well, we've seen Griffith with the moon (not full) in the last page of 258... Another hint?!

Now to argue against myself a bit, I'd say that the fact the Brand didn't react at all is odd, and that I'm not convinced it could be suppressed. Yet Schierke didn't feel anything either in spite of the Child's incredible power (except for a vague "strange Od" emanating from him), so that argument retains some validity because it's very strange overall. But there's also his astral representation. It's clearly a kid, not a Hawk or anything. So that means it changes automatically, can be changed by the child/Griffith, or that both are separate entities. It seems to be made of solid light though, that could easily be related to Griffith again. And it also "appeared" suddenly when the group was in danger, as if the Child had chosen to reveal his power because he had no other choice. That lends more strength to the "suppressed power" theory. Bah.