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Our research presents theoretical and numerical investigations of the dynamics and thermal transport properties in various locally resonant nanophononic metamaterials. Using finite element analysis, we show that the hybridization between the local resonances of the branched nanopillars and the bulk phonon modes of the host nanostructure can alter the phonon dispersion spectrum and greatly reduce the group velocities, leading to significant thermal conductivity reduction. According to the configuration of the periodic nanostructure, we propose a cantilever-in-mass model to theoretically analyze and control the resonance hybridization band. The influence of nanopillar number and size on the resonance hybridization frequency is systematically explored by both theoretical analysis and numerical simulation. Excellent agreement between theoretical results and numerical simulations reveals that the locally resonant frequencies can be accurately predicted by the proposed analytical model. Remarkably, the thermal conductivity of the resonant branched nanostructure can be tailored close to zero at the vicinity of local resonances with flat dispersion curves.