Abstract: This study focused on ten natural evergreen broad-leaved mixed forests in Kaihua County, utilizing continuous forest inventory data from 2019 to investigate the differences and mechanisms of ecological niches and competition among nearest neighboring trees with varying kinship relationships. The neighborhood analysis tool in ArcGIS was employed to identify nearest neighboring trees and calculate competition indices, ecological niche overlap, and similarity. Phylogenetic classification(phylum, class, order, family, genus, and species) was applied to quantify kinship relationships. Non-parametric Kruskal-Wallis tests combined with Dunn’s post hoc analysis were used to compare differences in competition indices, niche overlap, and similarity across kinship categories. A mediation effect model was constructed to explore how kinship relationships influence competition intensity through niche characteristics. The results revealed that: Conspecific nearest neighbors exhibited significantly higher competition indices than other kinship types. Ecological niche overlap and similarity increased with closer kinship relationships. The competition index between nearest neighboring trees was significantly higher when the niche overlap and similarity level reached grade IV(0.75～1.0) compared to those in grade I(0～0.25), grade II(0.25～0.5), and grade III(0.5～0.75). Kinship relationships indirectly affected competition intensity by mediating niche overlap and similarity. These findings provide novel insights into how kinship, niche differentiation, and competition collectively shape species coexistence in forest ecosystems.