The Braun family is an Eldian family residing in Liberio. Reiner Braun, the inheritor of the Armored Titan, hails from this family, as well as Gabi Braun who is likely to inherit the Armored Titan next.
History: At some point, Karina met a Marleyan man and later gave birth to Reiner in 833. However, unions between Marleyans and Eldians are forbidden, so she had to remain in the internment zone with her son. Karina later revealed his origins to him and wished they were born Marleyans.
Story: As the Marley Mid-East War is coming to an end, the Marleyan army is fighting at Fort Slava. Gabi finds an opportunity to prove she deserves to become the next Armored Titan, and manages to blow up an armored train, which allows the Jaw Titan to penetrate their enemy's defenses. As the Armored Titan, Reiner joins the battle and proceed to kill the remaining soldiers.
Source: Braun family (Anime), available under CC BY-SA 3.0.