YOU SAID:

I ain't never seen two pretty best friends, always one of them gotta be ugly.

INTO JAPANESE

私は2人のかわいい親友を見たことがない、常にそのうちの1人が醜くなければならない。

BACK INTO ENGLISH

I've never seen two cute best friends, always one of them must be ugly.

INTO JAPANESE

私は2人のかわいい親友を見たことがない、常にそれらの1つは醜いに違いない。

BACK INTO ENGLISH

I've never seen two cute best friends, always one of them must be ugly.