Future solicits call the two kids the Children of Eternity. Before i actually SAW them, i assumed it was just a name, of some kind of cult or something... but now it looks as though they are the LITERAL children of the character Eternity,
who also has the whole star motif, and sometimes has yellow speech balloons. I am not sure about cloak guy though, Eternity himself is usually more.... grandiose. But it could be him. Loki is in the Halls of All Knowing there, the library of the gods, which seems like a place Eternity might actually visit on occasion. I doubt it is Billy, personally, I think it's more closely related to Eternity even if it's not actually him, but some kind of aspect or something, it fits better with the whole time shenanigans going on. Here's pics so you can judge for yourselves, though: