On 29 October 1845, he moved to London, calling himself Julius Josaphat. On 16 November 1845, he converted to Christianity in a ceremony at St. George's German Lutheran Chapel in London, and changed his name to Paul Julius Reuter. One week later, in the same chapel, he married Ida Maria Elizabeth Clementine Magnus of Berlin, daughter of a German banker.
In 1845, Reuter married Ida Maria Magnus, daughter of Friedrich Martin Magnus, a German banker in Berlin. They had three sons: Herbert, who became the 2nd Baron (succeeded by his son Hubert as 3rd Baron), George and Alfred. Clementine Maria, one of his daughters, married Count Otto Stenbock [sv], and after Stenbock's death, Sir Herbert Chermside, a governor of Queensland.