YOU SAID:

I am a big boy, if my brother hits me on the head I become a small boy

INTO JAPANESE

私は大きな男の子です。兄が頭を殴ると小さな男の子になります。

BACK INTO ENGLISH

I'm a big boy When my brother hits his head, he becomes a little boy.

INTO JAPANESE

私は大きな男の子です兄が頭を打つと、彼は小さな男の子になります。

BACK INTO ENGLISH

I'm a big boy When my brother hits his head, he becomes a little boy.