Grant akaberekerwa muNew York City, New York, mwanakomana waGabriel Grant, chiremba uye chiremba weAmerican Civil War, naCaroline Manice. Amai vaMadison Grant vakanga vari muzukuru waJesse de Forest, muHuguenot weWalloon uyo muna 1623 akaunganidza boka rokutanga revagari vemo kuti vagare muNew Netherland, nharaunda yeDutch Republic paAmerica East Coast. Kurutivi rwababa vake, tateguru vokutanga veAmerica vaMadison Grant vakanga vari Richard Treat, mutungamiriri wePitminster Church muEngland, uyo muna 1630 akanga ari mumwe wevagari vokutanga vePuritan veNew England. Madzitateguru aGrant kuburikidza nemutsara waTreat anosanganisira Robert Treat (gavhuna wekoloni yeNew Jersey), Robert Treat Paine (asinaina Chirevo cheRusununguko), Charles Grant (sekuru vaMadison Grant, akashanda semukuru muhondo ya1812), naGabriel Grant (baba vaMadison), chiremba akakurumbira uye komisheni wehutano weNewark, New Jersey. Dr. Gabriel Grant akapiwa Medal of Honor paakanga achishanda somuvhiyi ne2nd New Jersey Volunteers muHondo Yenyika Yose. Mukati meHondo yeFair Oaks
, akaendesa vakakuvadzwa kunzvimbo yakachengeteka apo akanga ari pasi pemoto unorema. Grant akanga ari mugari womuNew York City kwoupenyu hwose.