Composites with ferroelectric and non-ferroelectric phases were synthesized by changing the volume percent of the phases and the dielectric properties were investigated. New factors influencing the dielectric permittivity of the composites were considered for the application and design of high performance dielectric composites. The percolation limit, which depends on the morphology and connectivity of the phase, showed similar values for Pb0.7Ba0.3(Zn1/3Nb2/3)O-3 - Pb1.83Zn0.29Nb1.71 O-6.39 and BaTiO3-Ba6Ti17O40 diphasic composites. However, the critical point for Pb0.7Ba0.3(Zn1/3Nb2/3)O-3-Pb1.83Zn0.29Nb1.71O6.39, which exhibited a dielectric anomaly, had a lower value than that of the percolation limit. The dielectric anomaly, which was observed below the percolation limit, is believed to be caused by a factor that can propagate any ferroelectric lattice vibration mode from the isolated ferroelectric phase to the non-ferroelectric matrix. The dielectric anomaly seems to depend on the connection between oxygen octahedra. Therefore, when the oxygen octahedra make a three-dimensional connection by corner sharing in the composite, the dielectric anomaly appears even when the volume percent of the ferroelectric phase is low. In particular, in Pb-based systems such as Pb0.7Ba0.3(Zn1/3Nb2/3)O-3-Pb1.83Zn0.29Nb1.71O6.39, the critical point exhibited the lowest value because the highly polarizable Pb2+ ions may also contribute to the propagation of the ferroelectric lattice vibration mode.