水乳交融

Explanation: Blend: blend together. Like water and milk together. Analogy or a combination of feelings are very close harmony. 　　Usage: The main predicate; as the predicate attribute, complement; with compliment 　　Source: Qing Xia's "flavor of": "Although previous studies have intimacy between men and women, this time is in harmony carry on." 　　Examples: A few days work, with Wuren're getting ~. (Qing Liu E, "Travels" Nineteenth back) 　　Riddle: Tea; powdered milk Thesaurus:  be bound together like brothers and sisters, Auxiliary car dependency, be finger and glove with sb., brotherliness, Trinity, As close as body, One turn, brotherly feeling