Kenji is the son of Namie, who is Hiroshi's sister. Akira is Hiroshi's nephew, which means Akira's parent is Namie or another sibling of Hiroshi not mentioned in the problem. Considering that Sato never had children, it is safe to conclude that Namie is Akira's mother. Therefore, Kenji and Akira are first cousins because their mothers are sisters.

Sato is Hiroshi's sister, which means her relationship to Kenji and Ayumi is as their aunt. Sato is the sister to their mother Namie, which makes Sato the aunt to Namie's children.

Ayumi, being the daughter of Namie and the niece of Hiroshi, has Hiroshi as her uncle. Since Hiroshi is Akira's uncle, and Namie is the implied mother of Akira, Ayumi too is a cousin to Akira, similar to Kenji, because they share the same maternal lineage through Namie.
Hiroshi is Akira's uncle, and he has a sister named Sato who has never married or had children. Hiroshi's other sister, Namie, has two children, a son Kenji and a daughter Ayumi. How is Kenji related to Akira and Sato, and what is Ayumi's relationship to Hiroshi?

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