No, Upper Rank 1 is not related to Tanjiro in any way.
Upper Rank 1, also known as Kokushibo, is a powerful demon who is one of the Twelve Kizuki. He is not a relative of Tanjiro or anyone in his family.
Tanjiro's family is known to be a family of demon slayers, and he is the only known survivor of his family after they were attacked by Muzan Kibutsuji, the demon king. Kokushibo is an antagonist who poses a significant threat to Tanjiro and his companions in the Demon Slayer Corps.
