John F. Kennedy Jr.’s friends knew something was up when they saw a limousine pull up to his gray, shingled Cape Cod cottage. John grew up in that house — his family spent nearly every summer in Hyannis Port in the home his parents bought for $45,948 in 1957. The place was one of three houses making up the so-called Kennedy Compound, along with John F. Kennedy Jr.’s grandparents’ house on the Nantucket Sound — the Big House, as the family called it — and the house his aunt Ethel once shared