Ọ bụ nwa nwoke nke William H. Gates Sr. (b. 1925) na Mary Maxwell Gates (1929<unk>1994). Nna ya bụ onye ọka iwu a ma ama, nne ya jere ozi na ndị isi oche nke First Interstate BancSystem na United Way. Nna nna nna Gates bụ J. W. Maxwell, onye isi oche nke ụlọ akụ mba. Gates nwere otu nwanne nwanyị, Kristi (Kristianne), na nwanne nwanyị, Libby. Ọ bụ onye nke anọ nke aha ya n'ezinụlọ ya, mana a maara ya dị ka William Gates III ma ọ bụ "Trey" n'ihi na nna ya nwere "II" ASX. Ezinụlọ ahụ bi na mpaghara Sand Point na Seattle n'ụlọ nke ajọ ifufe mebiri mgbe ọ dị afọ asaa.
nwanne m nwaanyị nke tọrọ m, bụ́ Kristi (Kristianne), na nwanne m nwaanyị nke m tọrọ, bụ́ Libby