INTRODUCTION: In the United States, many men of color experience poor health outcomes and confront serious healthcare obstacles. Yet, little research and few interventions have addressed men's relationships and their influence on healthcare behaviors. METHODS: This study analyzed a male lay health advisor (LHA) intervention dataset with 227 North Carolina African-American and Latino LHAs and their "Confidants" (men they reached). This study aimed to: (1) examine racial/ethnic differences in Confidant-LHA relationship interdependence properties, (2) assess the concordance of data obtained from three one-item closeness measures, and (3) test Confidant-LHA relationship interdependence and LHA preventive health behavior effects on Confidant preventive health behaviors. These behaviors included healthcare visits, fruit and vegetable consumption, and condom use frequency. Relationship properties were diversity, length, interaction, and closeness. Closeness measures included the Inclusion of Others in Self (IOS) pictorial scale, an adapted, and a verbal equivalent IOS scale. Kendall's tau test evaluated correspondence among three closeness measures. Hierarchical generalized linear regression analyses tested association between covariates and Confidant preventive health behaviors. RESULTS: No racial/ethnic differences were found for any relationship property mean values, other than interaction frequency. Latinos interacted with one another more frequently than African American counterparts. Strong correspondence existed among responses of three closeness measures: original IOS versus an adapted IOS scale [[tau]=0.636 (p<.001)], and adapted IOS versus verbal equivalent IOS scale [[tau]=0.602 (p<.001)]. Confidant-LHA closeness was correlated with longer familiarity, more frequent interactions, and more diverse interpersonal connections. LHA closeness to Confidant had a significant positive association (p<.05) with Confidant closeness to LHA. A significant interaction effect existed between LHA healthcare visits and Confidant-LHA closeness (p<.05): increased Confidant closeness to LHA strengthened the positive relationship between LHA and Confidant healthcare visits. CONCLUSIONS: Comparable relationship interdependence findings between African-American and Latino participants suggest similar receptiveness to social support and influence interventions like LHA programs. Strong correlation between adapted and original IOS closeness measure supports exploring the validity of this adapted IOS measure with similar populations. Finally, links between LHA and Confidant preventive healthcare visits supports future male LHA interventions to examine the most efficacious Confidant-LHA relationship for improving men's health outcomes.