This research discusses the optimization of capacity and locations for multi single-phase distributed generation (DG) in unbalanced distribution systems to reduce power losses, improve bus voltage while maintaining voltage imbalances and harmonics within the acceptable limits. The optimization of single-phase DG uses new enhanced symbiotic organism search (NeSOS) based genetic algorithm (GA) operator. NeSOS is developed by modifying the mutualism and commensalism phases using the random weighted inverse vector. The parasitism phase is modified by introducing sub-phase in parasitism phase. NeSOS based GA operator is validated using the IEEE 33bus system and tested using an unbalanced 25-bus distribution system. Validation using the IEEE 33-bus distribution system shows that NeSOS based GA operator produces the lowest power loss compared to, chaotic moth-flame optimization (CMFO) based power loss sensitivity factor (PLSF), particle swarm optimization (PSO), improved analytical (IA), loss sensitivity factor (LSF), and hybrid PSO method. Simulations using an unbalanced 25-bus distribution system indicate that NeSOS and SOS successfully reduces active and reactive power loss by 68.24% and 64.93% respectively, however in terms of convergence rate, NeSOS is, on average, 52.39% faster than SOS.