Saint Nektarios was born on October 1, 1846 in Selybria of Eastern Thrace. At Holy Baptism he was named Anastasios Kephalas. His parents, Demos (Demosthenes) and Balou (popular for Vasiliki) Kephalas, were simple, poor and pious Christians. Demos was from Ioannina and Vasiliki, whose maiden name was Triandafyllidou, was from Selybria. Anastasios was the fifth of six children: Demetrios, Gregory, Smaragda, Sevasti, Mariora and Haralambos (his name appears in the will of the Saint, but some sources say he replaced the Saint as teacher in the village of Lithi in Chios). They brought him up in a manner pleasing to God, and did what their very limited means allowed for his formal education. His first letters were taught to him by his mother, which she based on the writings of the Church. Thus, when his mother taught him Psalm 50, he liked to repeat the verse: "I shall teach thy ways unto the wicked and sinners shall be converted unto thee."
Mariora Kephalas was a sister of Saint Nektarios. Probably for health reasons, the Saint brought her from Selybria to Athens. She only lived a short while in Athens, since in 1900 she died from breast cancer. The Saint faced this illness of his sister alone, together with her death and burial. He bought for her a grave, which was a unique luxury in those days, at the First Cemetery of Athens, where his sister is buried.