Gamma ray detected high-redshift blazars (z>3) are intrinsically interesting since they inform us about the evolution of gamma-ray blazars and are, by definition, some of the more luminous blazars in the Universe. It has been found in many studies that such high z blazars host extremely massive black holes ($M_{\rm BH}> 10^{9} {M_{\odot}}$) and thus shed a new light on the formation of supermassive black holes in the early Universe. Here we report the first detection of gamma-ray emitting blazars beyond z=3.1 using the sensitive Pass 8 dataset of Fermi-LAT. These objects are found to host extremely massive black holes at their centers, as confirmed from both IR-UV continuum modelling with a standard accretion disk and also with the emission line measurements using optical spectroscopy. Further details of the results will be presented within the framework of the disk-jet connection in powerful jetted AGNs.