Brian was the third of 12 children; Gearóid, Ciarán, Roisin, Fergus, Kevin, Maeve, Nessa, Nuala, Sheila, Niall, and Micheál (in that period, known as the Gaelic Revival, giving one’s children Gaelic names was somewhat of a political statement.) Though relatively well-off and upwardly mobile, the O'Nolan children were home-schooled for part of their childhood using a correspondence course created by his father, who would send it to them from wherever his work took him.