Michael has a very challenging and unique relationship with his family in the first film of The Godfather trilogy. Michael is the most beloved of the three children. Vito Corleone is one who shows this, as he refuses to take the family picture "without Michael." For his part, Michael understands this, but he also seeks to establish his own identity apart from his family. When eating lasagna with Kay, Michael tells her the story of Johnny Fontaine and Luca Brazzi and how his father was instrumental in helping the singer early on in his career. When Kay expresses her horror at what she is hearing, Michael looks in the distance and tells her, "That's my family, Kay- it's not me." In this, Michael establishes himself early on as one who seeks to divorce himself from the path of the family and its embrace of the mafia ways.
All this changes when an attempt is made on Vito's life. Michael's visit to his father while he is in the hospital is a critical moment, for it is the first time that Michael shows himself to be capable of moving towards ends that represent the sinister side of the family. Yet, he does so for defense of his father. Being a victim of police brutality and enlisting the help of nurses and family bakers to help his father becomes a part of this. When Michael hatches the plan to kill the police chief, McCluskey, and the drug overload, Solozzo, in order to protect his father, it is the first time that he overtly abandons his promises to Kay that he is different than his family. When he returns from his time abroad, Michael assumes a different role in the family, one in which he aligns himself with his father as consigleri, or family adviser. Michael becomes fully associated with the Corleone name, to the point where he consolidates his own power with the execution of the other heads of the five families. When Michael tells Kay, in the most direct of ways, not to "ask about my business," and then proceeds to lie to her about his own involvement with Carlo's execution, it is a telling sign that Michael has become "the Godfather," completely aligning himself with the family he once detested, and becoming everything he once hated. The door closing on Kay is a moment where Michael has symbolically closed the door on his past resentment. He is the family.