(mentions of child abuse) Sherlock and John have been skating around the subject of starting a family for months , John always becoming distant as soon as it comes up, and now that Sherlock wants to talk to him about adoption, John is even more hesitant. Because while he knows in his heart that he would want to raise a child with Sherlock, he is deeply terrified of becoming like his father. His father was an angry, violent man that made John's childhood a living nightmare, and John knows that he has some of his father's temper in him and he just can't bear the thought of one day putting his own child through the same hell without even realizing it. Cue Sherlock helping him through these thoughts until John no longer doubts himself.