I was just curious about something I've observed in three anime series: Fullmetal Alchemist, Inuyasha, and Trigun. In each of these series there is a character (usually leading) that has lost an arm in some physically violent incident with a sibling. Edward Elric from FA loses his right arm (along with a leg) performing forbidden alchemy with his younger brother, Alphonse (who loses his entire body). Sesshomaru of Inu loses his left arm (paw) in a battle over Tetsusaiga with Inuyasha. In Trigun, Knives relieves Vash (his twin) of his left arm prior to the July City catastrophe.
Is there some sort of underlying symbolism or cultural significance to these occurrences of corporeal dismemberment, in particular amputation of an arm, while a sibling is present in a physically violent situation?
Thanks for any help you give! ;)