Two dimensional carbon allotropes with multiple atomic layers have attracted significant interest recently. In this work a new three atomic layer thick 2D carbon allotrope, twin T-graphene, is proposed. The sp2 hybridized dynamically stable phase is a nonmagnetic semiconducting material with an indirect band gap of 1.79 eV. Thermal stability investigations indicate that the material undergoes no change in the bonding pattern at 2000 K. The study of its mechanical properties indicates that it is an elastically isotropic soft material with low values of elastic constants. The electron mobility of the semiconductor is found to be nearly 375 cm2 V-1 s-1. The material when doped with single nitrogen in the tetragonal site undergoes a drastic change in its electronic properties and manifests itself in the form of a bipolar magnetic semiconductor which is a potential spintronic material. The study of the optical properties clearly indicates an optical gap of 1.89 eV. The material shows optical response in the visible range. Two sharp characteristic EELS peaks indicate the presence of this material. All these characteristics indicate that this material can have potential photocatalytic activity and be an attractive material for the applications in field effect transistors.