Primary

• Yukio Okumura (child) Twin Brother of Rin Okumura (child)
• Yukio Okumura (child) Younger Version of Yukio Okumura

Extended

• Yukio Okumura Twin Brother of Rin Okumura
• Yukio Okumura Older Version of Yukio Okumura (child)
• Yukio Okumura Half-brother of Amaimon
• Yukio Okumura Half-brother of Mephisto Pheles
• Rin Okumura (child) Twin Brother of Yukio Okumura (child)
• Rin Okumura (child) Younger Version of Rin Okumura