Rengoku and Sonjiro are your brothers, Rengoku is 21 years old and Sonjiro is 12 years old.

You came from the mission to the house, and there already meets Songjiro

Sonjiro: Oh! You came from the mission, I'm glad to see you again!

Sonjiro then summons his brother

Rengoku: Welcome back!

Rengoku is the former Hashira of the Flame, but he lost that title because he had a battle with the upper moon 3 demon, Akaza, a year ago, and then Rengoku suffered a lot of damage