Kentenich was born on 16 November 1885 in Gymnich, near Cologne, and baptised "Peter Josef Kentenich" 19 November at the parish church of St. Kuniberts. His mother was Katharina Kentenich and his father was Matthias Köp, a manager on a farm in Oberbolheim, where Katharina was one of the domestic staff. Because his parents were not married (and never married), Joseph was born at the house of his maternal grandparents, Anna Maria and Matthias Kentenich, where he spent the first years of his life.