
Background: Despite the efforts to prevent the spread of HIV/AIDS through programme interventions targeting individuals, the persistent high rates of HIV/AIDS through heterosexual relationships in Nigeria further underscores the need to examine the effects of relational variables such as sexual intimacy on sexual behaviours, multiple partners and HIV/AIDS risk. It has been acknowledged that sexual networking could influence the spread of HIV, however, the role of relational variables in the spread of HIV amongst stable relationships, and sexual networks remains unclear. Hence the focus of this study is on sexual intimacy and HIV risk amongst sexual groups such as dyad, triad, or more partners in Nigeria, where high numbers of new HIV/AIDS infection are within marital or cohabitation relationships. Methods: A sample of 1,621 (864 women; 757 men; 815 HIV seropositive; 806 HIV seronegative) respondents, who participated in survey and in-depth interviews, were selected from two clinics and two other locations using multi-stage and purposive sampling methods. SPSS (version 21) software was used for quantitative data analysis while the qualitative data was analysed quantitatively. Results: Age (P = 0.05), sex (P = 0.001), education (P = 0.017), relationship status (P = 0.000), number of sexual partners (P = 0.000), had sex while drunk (P = 0.000) and HIV status (P = 0.000) significantly correlate with levels of sexual intimacy. Relational variables provide a better understanding of complex sexual behaviours in sexual groups and HIV/AIDS risk. Conclusion: The levels of sexual intimacy are the relationship pathways through which factors such as age, sex, relationship status, number of sexual partners, education, had sex while drunk and HIV status influence sexual behaviours and HIV risk amongst groups. Targeting sexual groups instead of the individual to curb the spread of HIV in high incidence areas would be more rewarding. Hence there would be improvement in the sexual wellbeing of the individuals and the public.