We’ve seen war turn brother against brother in the world of Westeros before, but House of the Dragon’s eighth episode introduced viewers to a new pair of siblings with a fan favorite story that ends in heartbreak. Arryk and Erryk Cargyll are identical twins from a small house in the crownlands outside of King’s Landing. In George R.R. Martin’s Fire & Blood, the Cargyll boys are members of Viserys’ Kingsguard who take opposite sides in the Dance of the Dragons’ war between Princess Rhaenyra’s blacks and Queen Allicent’s greens. So identical, even their fellow Kingsguard couldn’t tell them apart, Arryk and Erryk seemed to have a loving relationship and were largely inseparable before civil war broke out. Both brothers saw a lot of the inner workings of the royal family because of their position and early on, it is clear that Erryk, at least, takes issue with Aegon II’s general whoring and behavior unfitting for a king.  Arryk seems a bit more apathetic to royalty and humankind’s general baser nature seems to care less for politics and more for the commonfolk’s concerns, like keeping the price of beer low. Ultimately, the two brothers will make their fateful choices and walk different roads in the war ahead before their paths will cross one last time and make sad history.  After Viserys’s death, Arryk aligned himself with Aegon II and continued to work under Lord Commander Criston Cole on the Kingsguard. Erryk, however, left The Red Keep and joined Rhaeyna and Daemon on Dragonstone as a member of Rhaenyra’s queensguard. Criston Cole enlisted Arryk’s help in infiltrating Dragonstone while pretending to be his twin brother, so he could get close to Rhaenyra and her children and assassinate the rebellious Targaryens.  However, Cole’s plan goes wrong when Erryk stumbles across his twin brother in a hallway beneath the citadel and an epic sword fight between the two brothers begins. When Arryk and Erryk face off against each other, their sword fight will become the stuff of bard’s songs. Many decades later, Lady Olenna Tyrell even had a pair of twins named Arryk and Erryk on her personal guard. (Though in the Queen of Thorns biting style, she never bothered to learn their names, calling them instead Left and Right.) Both Cargyll brothers were seasoned warriors but what makes the twins’ story last through history is the very sad end, inspired in part by another pair of brothers from King Arthur’s time.  Unlike other Westerosi brothers at war – namely Game of Thrones’ Sandor and Gregor Clegane – Erryk and Arryk are more tragic because they are both basically decent, loyal men who want to protect their rightful monarch, realizing too late that it means losing what they personally love the most. New episodes of House of the Dragon premiere Sundays at 9 p.m. ET on HBO and HBO Max in the U.S. and Sky Atlantic in the U.K.