Umber is somewhat confirmed. There is evidence that he wanted to be with Quibli (granted it was a one line thing when Moon read both his and Kinkajou’s [hopefully I spelled that right] mind at the same time). However this is the last book Umber appears in and then he disappears off the face of the earth. He’s not dead, just gone, no one knows what happened to him. Peril however isn’t even close. I don’t think Tui thought about it considering Peril is introduced super early in the series. Sky is introduced much later in terms of main books go and he’s assumed to be Peril’s lost twin that was sacrificed to save her. One problem is, Sky is a boy, Peril is a girl, and supposedly they both came from the same dragon egg (fits because Sky has no fire and Peril has firescales). Neither of them appear to be trans or written with that in mind though so I don’t really understand the theory.