The primary objectives of this study are to evaluate the steady-state pharmacokinetics (PK) and confirm the dose of cobicistat-boosted atazanavir (ATV/co) or cobicistat-boosted darunavir (DRV/co) in HIV-1 infected antiretroviral treatment-experienced, virologically suppressed, pediatric participants between the ages of 3 months to < 18 years of age.