Hiroshi is the son of Yuto and Aiko. Yuto is Keiko's brother, and Keiko is the wife of Akira, making Yuto Akira's brother-in-law. Consequently, Hiroshi is the nephew of both Akira and Keiko.

Yumi, on the other hand, is the daughter of Hana, who is Kenji's sister. Since Kenji is the son of Akira and Keiko, Hana is also Akira and Keiko's daughter. This makes Yumi their granddaughter.

For the relationship between Hiroshi and Yumi: Hiroshi's father, Yuto, is the brother of Keiko, who is Yumi's grandmother. This makes Hiroshi and Yumi first cousins once removed, where Hiroshi is one generation removed from Yumi, as he is the cousin of Yumi's parent, Hana.
Akira is Kenji's father. Kenji has one sibling, a sister named Hana. Hana is married to Taro, and they have two children: Yumi and Satoshi. Akira's wife, Keiko, has a brother named Yuto. Yuto is married to Aiko, and they have a son named Hiroshi. How are Hiroshi and Yumi related to Akira and each other?

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