Ethan and Aiden are twin brothers.
Little is known Ethan and Aiden's early life, except that they were apparently bitten at a somewhat young age (according to writer Will Wallace) and that the fact that they're twins allowed them to merge together into one extra-large Werewolf, an ability they had difficulty controlling for a long time. Much of their youth and adolescence was spent living as Omegas who ran with a bloodthirsty pack led by a ruthless Alpha who abused them and made their lives miserable. At some point, they eventually met Deucalion, who had recently become the self-proclaimed "Demon Wolf," after killing his own Betas and becoming an Augmented Alpha. Deucalion decided to not only teach them how to control their merged Werewolf form, but to also learn how to fight so that they would be able to join his Alpha Pack. However, all members of the Alpha Pack were required to be Alphas who have slaughtered their own packs as initiation, just as Deucalion, Kali, and Ennis had done before the pack's creation, and since Ethan and Aiden were still Omegas, they needed to kill their entire pack in order to gain membership. Feeling indebted to Deucalion for all the help he had given them, Aiden and Ethan made the decision to join the Alphas and merged into their Twin Alpha form to slaughter the Betas and Emissary of their pack before finally going after their Alpha, who allegedly begged for his life before they tore him apart. ("The Girl Who Knew Too Much")
Afterward, the twins joined the Alpha Pack under Deucalion's leadership, though Aiden would later admit that the pack wasn't as democratic as one would think. At some point in 2011, Deucalion learned that Derek Hale had killed his uncle Peter and replaced him as the Alpha of the Hale Pack, piquing Deucalion's interest. Once they heard another rumor that Scott McCall had the potential to become a True Alpha, the most rare form of Alpha that appears only once a century at the most, Deucalion, hoping to add both a Hale Alpha and a True Alpha to his ranks to increase the pack's power, led the Alpha Pack to Beacon Hills to force Derek to slay his own pack and join them, paving the way to Scott in the process.
Ethan, like his twin Aiden, was an aggressive person who did whatever was necessary to survive. However, Ethan has never seemed to possess the quick temper and impulsive nature that his brother Aiden displayed frequently. Also like Aiden, Ethan enjoyed taking advantage of his new-found Alpha powers by dominating those around him to compensate for the powerlessness he felt as an Omega, carrying out Deucalion's every violent order, even if it was an act with which he disagreed. However, after he went undercover as a student at Beacon Hills High School, he slowly began to become a more sensitive person, especially after he started a romantic relationship with Danny Mahealani. This led him to be the first member of the Alpha Pack to start questioning his orders, especially when he started to get to know the members of what would become the McCall Pack.
Both Ethan and Aiden's association with the McCall Pack helped them to grow into more selfless and compassionate people who were willing to put their life on the line for their friends. In fact, Aiden ended up meeting his death while in a battle with an Oni demon to buy the pack time to defeat the Nogitsune, and though he gave up his life, he was able to kill the Oni in the process, proving to all who knew him that he did have the potential to be a hero.
Ethan and Aiden are both lean and muscular young men of medium stature, with slightly tanned white skin, reddish-brown hair, and hazel eyes, though Ethan is slightly taller and leaner than his twin, Aiden, though just as muscular. The twins preferred dressing in trendy clothing, choosing designer jeans, v-neck tshirts in various colors, black leather jackets, and motorcycle boots.