YOU SAID:

I have two little brothers, both of them younger

INTO JAPANESE

私には2人の弟がいて、どちらも年下です

BACK INTO ENGLISH

I have two younger brothers, both of whom are younger than me.

INTO JAPANESE

私には 2 人の弟がいて、どちらも私より年下です。

BACK INTO ENGLISH

I have two younger brothers, both younger than me.

INTO JAPANESE

私には 2 人の弟がいて、どちらも私より年下です。

BACK INTO ENGLISH

I have two younger brothers, both younger than me.