Close (relationship): having an intimate or friendly relationship with someone; used for friends, family, colleagues, etc.
あの二人は学生の頃から仲の良い友達だ。
Those two have been close friends since their student days.
うちの家族はみんな仲の良い家庭だと思う。
I think our family is a close-knit one.
先生と生徒が仲の良いクラスは雰囲気が明るい。
A class where teachers and students get along well has a bright atmosphere.