It is clear that Errett was a child prodigy but it was remarkable that he had a sister, Mary, who was two years younger than he was an was also a mathematical prodigy.
Ito ay malinaw na Errett ay isang anak-taka ngunit ito ay kapuna-puna na siya ay may isang kapatid na babae, Maria, na dalawang taon na mas bata sa siya ay isang ay din ng isang kagila-gilalas na matematiko.