Wilhelm Joseph Blos was born at Wertheim am Main during the aftermath of the 1848 uprisings, the son of a physician who had moved away from the big city on account of his delicate health. Aloys Blos died from an incurable lung disease in 1856, when his son Wilhelm was just seven years old. His children's mother almost immediately remarried, selecting on this occasion a forester. Wilhelm and his sister acquired a step-father who abused Wilhelm. In 1863 he went to live with his grandparents. His grandfather died almost at once, but his grandmother attended to his education. He became a pupil at the in Wertheim, his hometown, located slightly above 100 km to the north of Stuttgart. Wilhelm Blos would later sue his step-father successfully for stealing his inheritance. Meanwhile, he embarked on a commercial apprenticeship in Mannheim, but broke it off uncompleted in order to study for and pass his Abitur (school graduation exam) which in 1868 opened the way for him to enrol at the University of Freiburg to study History and Philology. At university he also joined the .