Brotherhood exists specifically to follow the manga. The 2003 anime caught up with Arakawa's serialisation while it was still running and invented its own second half with her blessing; Brotherhood, made after the manga finished, adapts all 108 chapters in order. That is why two long series of the same name exist and neither is a remake of the other in the usual sense: one is an original ending, the other is the author's. The Ishvalan war, the homunculi's origin, Father, and the Promised Day are the manga's and reach the screen only here.