Understanding the properties of interfaces and grain boundaries is pivotal for advancing the design and performance of modern materials and devices. The mechanical strength and durability of materials are significantly influenced by the integrity of these interfaces and grain boundaries. In this study, we employ density functional theory calculations to investigate the geometries, electronic properties, and mechanical behaviors of Σ3 (111) grain boundaries in Ni, AlNi3, and FeNi3 systems. Result reveals that these grain boundaries exhibit trigonal, hexagonal, and hexagonal close-packed structures with minimal bond length distortions, attributed to specific misorientation angles of 60°. They also demonstrate bonding characteristics akin to their corresponding polycrystalline bulk materials, indicating stability and twist character with anti-phase boundaries. Evaluation of grain boundary energetics indicates low energy values and stability across the studied systems. Furthermore, we conduct a detailed examination of the interfacial grain boundary structures of Σ3 (111) Ni/AlNi3 and Σ3 (111) Ni/FeNi3, revealing trigonal closed space configurations with twist character and anti-phase boundaries. Electron localization in interfacial regions suggests a metallic nature of interfacial bonds, supported by density of state calculations and positive Cauchy pressure. Assessment of mechanical properties indicate ductile behavior due to structural heterogeneity, moderate anisotropy. Overall, present study underscores the enhanced mechanical properties resulting from heterogeneity, offering promise for future applications in advanced materials and devices. Additionally, a comparative analysis with highlights the advancements and contributions of this study to the existing body of knowledge.