As many users of this website will be aware, the Spanish custom is to use one's fathers surname in everyday contexts, but to use the surnames of both one's father and mother in formal circumstances (e.g. on official documents). Picasso was the surname of the painter's mother; his father's surname was Ruiz. He signed his early paintings Pablo Ruiz Picasso, but soon dropped the Ruiz component.
According to Wikipedia, this "does not seem to imply a rejection of the father figure. Rather, he wanted to distinguish himself from others; initiated by his Catalan friends who habitually called him by his maternal surname, much less current than the paternal Ruiz."
Picasso's father was himself a painter, who specialized in naturalistic depictions of birds and other game. For most of his life he was a professor of art at the School of Crafts in Málaga and a curator of a local museum. His ancestors were minor aristocrats. The family of Pablo Picasso's mother, María Picasso y López, came from Liguria, a coastal region of north–western Italy (with Genoa as its capital). Pablo Picasso's full name (given on his birth certificate) includes over a dozen words, not including 'de la', 'de los', etc.
© Haydn Thompson 2021