Aaron Menahem Asimov, born about 1865. Asimov's grandfather on his father's side
First born son of Mendel Asimov, who was the son of Abraham Ber by his first wife, who was the son of Judah Asimov, Asimov's great, great-great grandfather.
Aaron's first born child was a girl who died in infancy. His second child was a boy, who would become Asimov's father.
Judah Asimov, Isaac Asimov's father.
Judah Asimov was born around December 21, 1896. (Russia at that time used the Julian calendar rather than the Gregorian calenadar, and Jews used their own lunar calendar, anyway).
He entered Hebrew School - in Petrovichi - at the age of 5. There were ten boys in the school, and of course no girls. Judah went to school there until he was 16. After that he received advanced instruction in the Talmud from the rabbi, and that was th extent of his formal education.
In his childhood, there was a Gentile girl of about 12 or 13, who had lived in the house for about 4 years, who took care of him. (Asimov doesn't give any other details). She "spoke Yiddish like a Jew, and even learned all the prayers in perfect Hebrew so she could supervise young Judah at his homework."
Asimov reveals part of his father's character, "It would never occur to him at any time in his life to save another person's face, or to let some small error go if it were unimportant." His father was always right, even when he aws wrong. (Asimov was like this also when he was young, but grew out of it.)
In 1916, Mendel (then in his 70s, Asimov estimates) fell sick. Judah, age 19, was in Borisoglebsk on a business matter, some 450 miles away. By the time he returned to Petrovichi, his grandfather was dead.
As for Asimov's grandmother, this is what his father told him (in letters that he wrote to Asimov at Asimov's request, when Asimov was much older and living in Boston): "She came from a family in which her mother counted for more than her father. Her father was a very simple man but a very honest and pious one. My grandmother, his wife, lived to a great old age, passing, I believe the hundred mark. She had 8 children, 3 girls and 5 boys, with my mother the oldest."
Nowhere, continues Asimov, "does my father tell me his mother's name. I learned it from another source. It was Anna Chaya."
In Memory Yet Green, by Isaac Asimov