Leonardo was born on 15 April 1452 (Old Style) "at the third hour of the night" in the Tuscan hill town of Vinci, in the lower valley of the Arno river in the territory of the Medici-ruled Republic of Florence. He was the out-of-wedlock son of the wealthy Messer Piero Fruosino di Antonio da Vinci, a Florentine legal notary, and Caterina, a peasant. Leonardo had no surname in the modern sense - "da Vinci" simply meaning "of Vinci"; his full birth name was "Lionardo di ser Piero da Vinci", meaning "Leonardo, (son) of (Mes)ser Piero from Vinci". The inclusion of the title "ser" indicated that Leonardo's father was a gentleman. Little is known about Leonardo's early life. He spent his first five years in the hamlet of Anchiano in the home of his mother, and from 1457 lived in the household of his father, grandparents and uncle in the small town of Vinci. His father had married a sixteen-year-old girl named Albiera Amadori, who loved Leonardo but died young in 1465 without children. When Leonardo was sixteen (1468), his father married again to twenty-year-old Francesca Lanfredini, who also died without children. Piero's legitimate heirs were born from his third wife Margherita di Guglielmo (who gave birth to six children: Antonio, Giulian, Maddalena, Lorenzo, Violante and Domenico) and his fourth and final wife, Lucrezia Cortigiani (who bore him another six children: Margherita, Benedetto, Pandolfo, Guglielmo, Bartolomeo and Giovanni). In all, Leonardo had twelve half-siblings, who were much younger than him (the last was born when Leonardo was forty years old) and with whom he had very few contacts, but they caused him difficulty after his father's death in the dispute over the inheritance. Leonardo received an informal education in Latin, geometry and mathematics. In later life, Leonardo recorded only two childhood incidents. One, which he regarded as an omen, was when a kite dropped from the sky and hovered over his cradle, its tail feathers brushing his face. The second occurred while he was exploring in the mountains: he discovered a cave and was both terrified that some great monster might lurk there and driven by curiosity to find out what was inside. Leonardo's early life has been the subject of historical conjecture. Vasari, the 16th-century biographer of Renaissance painters, tells a story of Leonardo as a very young man: A local peasant made himself a round shield and requested that Ser Piero have it painted for him. Leonardo responded with a painting of a monster spitting fire that was so terrifying that Ser Piero sold it to a Florentine art dealer, who sold it to the Duke of Milan. Meanwhile, having made a profit, Ser Piero bought a shield decorated with a heart pierced by an arrow, which he gave to the peasant.

Answer this question "What did his dad do" by extracting the answer from the text above.
Florentine legal notary, and Caterina, a peasant. Leonardo had no surname in the modern sense