Comment on the words "the boy's bitterness grew to rage." Why did the boy feel bitterness? Why did he fear the rage growing in him?​

We are a family of four. I live together with my mother Irina, my father Andrew and my brother Jim. We live  in a big apartment in the city. My mum is a housewife. She stays at home and does  all the house work - she cleans and cooks and does the laundry. That's why it is always nice and clean in our apartmen. My dad is an engineer. I am a pupil. And Jim is only six years old. I have always wanted to have a pet. Two weeks ago I had a bithday and my parents gave me a cat. I called him Tom. I like to spend time with my family.