YOU SAID:

My neighbour, whose aunt my brother lives next to, got sick.

INTO JAPANESE

兄の隣に住んでいる叔母の隣人は病気になった。

BACK INTO ENGLISH

The aunt's neighbor living next to his brother got sick.

INTO JAPANESE

彼の兄の隣に住んでいる叔母の隣人は病気になった。

BACK INTO ENGLISH

The aunt's neighbor living next to his brother got sick.