I have a question about whether those four cats were in the same litter or not.
I believe they may be, they have the same mother, and same father, and according to the wikia, they are all the same age (well not cinderpelt.) So my question is, are they in the same litter, or is it a mistake.
Brightheart and Thornclaw may have been punished, what I mean by that, their apprenticeship may have been delayed, so they couldn't train together, for the first few months if their training. The case may also be, that Erin Hunter may have failed to mention Brightheart and Thornclaw in Fire and Ice. Or it may be a wikia mistake, and they were not littermates after all. Let me know what you think.
UPDATE: I have just learned that Brackenfur and Cinderpelt were apprenticed early.