The actors — and real-life family — play father and son in a zippy new spin on the earliest years of the world's most famous detective. Ahead, the duo tell IndieWire about their on- and off-screen bond and giddily unpack a first season's worth of spoilers. [Editor’s note: The following interview contains spoilers for “ Young Sherlock .”] For Hero Fiennes Tiffin , “Young Sherlock” turned out to be an unexpected family affair. In the first season of the new Prime Video series, executive produced