Gates akaberekerwa muSeattle, Washington, musi waOctober 28, 1955. Iye ndiye mwanakomana waWilliam H. Gates Sr. (b. 1925) naMary Maxwell Gates (1929<unk>1994). Madzitateguru ake anosanganisira Chirungu, ChiGerman, ChiIrish, uye Scots-Irish. Baba vake vaiva gweta rakakurumbira, uye amai vake vakashanda pabhodhi revatungamiriri veFirst Interstate BancSystem uye United Way. Sekuru vaamai vaGates vaiva J. W. Maxwell, mutungamiri webhangi renyika. Gates ane hanzvadzi imwe yakura, Kristi (Kristianne), uye hanzvadzi duku, Libby. Ndiye wechina wezita rake mumhuri yake, asi anozivikanwa saWilliam Gates III kana "Trey" nokuti baba vake vaiva ne "II" yakakwana. Mhuri yaGates yaigara munharaunda yeSand Point muSeattle mune imwe imba yakakuvadzwa nedutu risingawanzoitika apo Gates aiva nemakore manomwe ekutanga muupenyu hwake.
nguva dzose aizoita purogiramu yepurogiramu zvakakwana