The first time I met him, he frowned and called her a crybaby.
Later, she showed him that she was actually very strong
He reluctantly called her sister
I don't know since when, he came to admit the wrong things she did, and he took care of the trouble she caused.
She was secretly proud of herself. It was a wise decision to recognize him as her younger brother when she was a child.
But, one day, he said I don't want to be your brother anymore.
He said he had grown up, but she never grew up