In Kenya similar to other countries in Eastern and Southern Africa There is a disproportionately high burden of the global HIV incidence among youth ages 15–24 years, and where adolescent girls and young women account for up to a third of all incident HIV infections and more than double the burden of HIV compared to their male peers. Previous work has shown early sexual debut as entry point into risks to sexual and reproductive health among young people including STI/HIV acquisition. This was a formative assessment of the local context of three sexual risk behaviors among youth ages of 15–24 years: early sexual debut, multiple sexual partnerships, and age-mixing /intergenerational sex for purposes of informing comprehensive combination HIV intervention program design. We conducted a cross-sectional formative qualitative study in four sub-counties within Homabay county a high HIV prevalence region of Kenya. Participants were recruited through youth groups, schools, government offices and, community gatekeepers using approved fliers, referred to a designated venue for focus group discussion (FGD). After oral informed consent, twelve FGDs of 8–10 participants were carried out. Transcripts and field notes were uploaded to Atlas.ti qualitative data analysis and research software (version 8.0, 2017, ATLAS.ti GmbH). Open coding followed by grouping, categorization of code groups, and thematic abstraction was used to draw meaning for the data. A total of 111 youth participated in the FGD, 65 males and 46 females. The main findings were that youth engaged in early sex for fear of being labeled ‘odd’ by their peers, belief (among both male and female) that ‘practice makes perfect’, curiosity about sex, media influence, need to prove if one can father a child (among male), the notion that sex equals love with some of the youth using this excuse to coerce their partners into premature sex, and the belief that sex is a human right and parents/guardians should not intervene. Male youth experienced more peer-pressure to have sex earlier. Female youths cited many reasons to delay coitarche that included fear of pregnancy, burden of taking care of a baby, and religious doctrines. Having multiple sexual partners and intergenerational sexual relationships were common among the youth driven by perceived financial gain and increased sexual prowess. HIV prevention strategies need to address gender vulnerabilities, as well as promoting a protective environment, hence application of combination prevention methods is a viable solution to the HIV pandemic.Trial registration number: The study was approved by the KNH/UoN Ethics review committee (KNH/UoN ERC-P73/03/2011) and New York University (NYU Reg no.–00000310).