Introduction Heterosexual relations among bisexual MSM engender spectrum of vulnerabilities for MSM as well as their partners. Socio-cultural pressure to marry may drive MSM to have female partners, indicating the potential for bridging HIV transmission. However, these interactions are poorly understood, and measurement of potential risk to MSM and their female partners is inconsistent in most of the South Asian countries. The study aims to analyse the overlapping male and female partnerships of MSM-SW given the multiplicity of risk for HIV.

Methods This paper uses data collected as a part of mapping and size estimation of MSM in Nepal, Bhutan, and Bangladesh and for India, the IBBA has been used (2010–2016). Analytical methods range from cross-country comparisons of tangible indicators to application of regression.

Results Bisexuality in the region is rampant as a substantial proportion of MSMs (42% in India to 74% in Bhutan) who have sex with a male in the last 6 months also reported to sleeping with a female partner during the same period. MSM age 20–29 years, who are never married and migrants are significantly more likely to have multiple female partners in each of the 4 countries. However, the considerably lower prevalence of condom use, among those having sex with multiple female partners in the last six months across the countries is a marker of the multiplicity of the STIs/HIV risk. Migration is playing an inverse role in determining the relationship with condom use in the last sex with female partner as those MSM who are non-migrants were more likely to use condom.

Conclusion Role of MSM-SW in HIV transmission is a more complex issue than depictions of men as sexual predators and women as uninformed victims. MSM programs should envisage beyond homosexuality and address bisexuality regardless of their sexual identity as threat clouding prevention efforts by increasing the thrust of programs designed for MSMs.