The Inner Circle is why people reread ACOTAR. Feyre didn't just find romance, she found her people. Rhys, Cassian, Azriel, Mor, Amren. That group of characters would die for each other, and they'd kill for each other, and somehow they still manage to be funny and broken and real. That's an exceptionally tight found family, and it's rare to find it replicated.
Six of Crows comes closest. The Dregs are a crew of outcasts who become more important to each other than anything else, and the way their relationships develop feels genuine. Kaz, Inej, Jesper, Nina, Matthias, Wylan. Each dynamic is different and layered. House of Earth and Blood has a similar vibe with Bryce and her circle. They're a motley crew of magical misfits who become family, and watching that bond develop is the heart of the book. An Ember in the Ashes features a found family that forms through hardship and shared purpose, and the loyalty between these characters is absolute. And Throne of Glass, despite being longer, builds one of the most beloved found families in YA fantasy. Celaena's relationships with Nehemia, Dorian, and Chaol create emotional anchors that last through the entire series. These books understand what makes found family resonate. It's not just that they're together. It's that they choose each other, repeatedly, even when it would be easier to walk away.