Leonardo Da Vinci had 17 brothers and sisters. All of his siblings were half-siblings.
There is not much mention of the siblings from his mother, but his father and the woman he married gave Leonardo seven brothers and sisters. Upon his father's death, which he received word of while beginning the "Mona Lisa," there was contention over his father's lands and belongings, resulting in Leonardo getting nothing that his father might have left for him. His uncle passed away around the same time, which came out more in Leonardo's favor, since he became the heir to his uncle's lands and belongings.