It is narrated from Abbad bin Abbad al-Muhallabi that he said: Among us, that is, the Muhallabis, I came across a woman who became a grandmother at the age of eighteen. She gave birth to a daughter at the age of nine, and her daughter also gave birth at the age of nine, so she became a grandmother at the age of eighteen.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العدد / 15417