YOU SAID:

It would behoove you to behave before your brothers come to the after party.

INTO JAPANESE

あなたの兄弟が二次会に来る前に、あなたは振舞うべきです。

BACK INTO ENGLISH

You should behave before your brother comes to the after party.

INTO JAPANESE

お兄さんが二次会に来る前に、あなたは行儀よくしなければなりません。

BACK INTO ENGLISH

Before your brother comes to the after party, you have to behave yourself.

INTO JAPANESE

お兄さんが二次会に来る前に、あなたは身だしなみを整えなければなりません。

BACK INTO ENGLISH

Before your brother comes to the second party, you have to take care of yourself.

INTO JAPANESE

お兄さんが二次会に来る前に、自分を大事にしなきゃ。

BACK INTO ENGLISH

I have to take care of myself before my brother comes to the second party.

INTO JAPANESE

弟が二次会に来る前に、私は自分の面倒を見ないといけない。

BACK INTO ENGLISH

I have to take care of myself before my brother comes to the after party.

INTO JAPANESE

兄が二次会に来る前に、私は自分の面倒を見なければならない。

BACK INTO ENGLISH

I have to take care of myself before my brother comes to the after party.