personally i think it was a slow burn (like how he said he only saw her as a childhood friend/sister) and his dysfunctional family definitely attributes to him wanting her affection
I don't think he had a crush on her when he was 15 and she was 10. It was more like a friendship and a person who saw him for who he is in that abusive household. Then they were apart for 7 years. I think the romantic interest started to develop after the met again, when she was 19 and he was 24
I just don’t understand how a 15 year old starts having a crush on a 10 year old. The age gap isn’t realistic