YOU SAID:

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

INTO JAPANESE

私は2人のかわいい親友を見たことがない、そのうちの1人はいつも醜くなければならない

BACK INTO ENGLISH

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

INTO JAPANESE

私は2人のかわいい親友を見たことがない、そのうちの1人は常に醜いに違いない

BACK INTO ENGLISH

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