Carl Joachim Hambro's lineage can be traced back to Rendsburg in the 1720s. The family was Jewish. The family member Calmer Joachim Hambro (1747–1806) relocated to Copenhagen in the late 18th century, and became a businessman. One of his sons, Joseph Hambro, moved on to London and founded Hambros Bank with his son Carl Joachim Hambro. Another son (and Joseph's brother) Edvard Isaach Hambro (1782–1865) moved to Bergen, Norway where he became a merchant in the early 19th century. Edvard Isaach Hambro fathered Carl Joachim Hambro (1813–1873), who in turn fathered the school manager Edvard Isak Hambro (1847–1909).