Louis Napoleon, the future Emperor Napoleon III, was fourteen years older than his first cousin Prince Napoleon. Notwithstanding this difference in age, an intimacy was established between them from an early date, and although at time a few clouds drifted over the atmosphere, nothing was ever to break the close connection binding them together. Their friendship, formed in a land of exile in which both passed their childhood and a portion of their youth, was proof against every trial, and endured up to the death of the Emperor.They were, however, very different in character, and in many points quite contrary to each other. In order to unfold the nature of this friendship, this work leaves aside official letters and keeps to those which reveal an intimate character. The reading of these letters, written with no eye to future publication, will assist the unprejudiced historian, more than anything else, to come to a true understanding of their real natures.