you're right bro, but let me correct you: "Past perfect occurs before simple past in a sentence"
the phrase that should be translated indicates to a time frame that had started somehow and it already ended but we don't know how.
my suggestion is comprised of three other sentences, that, two of them are kind of incomplete:
1.We were like sisters
2.we had lost each other but somehow we found each other..
3.we had been unaware of the other one till we finally met.
As far as i concern its not wrong to link this parts in a phrase without changing Grammatical tenses.
i just tried to deliver whole concept.