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So don't worry so much about how to use  had had  as a unit of grammar, they will come together naturally when you want to express the verb ' to have ' in the past perfect. Let's consider a different verb for a moment like  to want .
until up upon us very via viewer was we well were what whatever when whence whenever where whereafter whereas whereby wherein whereupon wherever whether which while whither whoever whole whom whose why will with within without would yet you your yours yourself yourselves