In anime, sibling bonds often take the shape of the most powerful of bonds to the greatest rivalries, but none are quite as tragic as Naruto‘s Uchihas and Demon Slayer‘s Shinazugawa brothers. Both the Uchiha and Shinazugawa families suffered devastating losses, leaving behind only a pair of brothers who became estranged and burdened by misunderstandings, loss, guilt, and painful decisions. While each pair of siblings carries the weight of these problems, the story of Genya and Sanemi is arguably more tragic.

https://screenrant.com/demon-slayer-most-tragic-sanemi-genya-sasuke-itachi/