Relations between the Kingdoms of Gondor and Arnor

The Realms-In-Exile were founded by the Faithful Numenoreans who survived the fall of Numenor in 3320 Second Age (SA). After the War of the Last Alliance (3434-41 SA) the relative standing of each throne changed, with Gondor growing to become a mighty power, whereas Arnor split into three seperate kingdoms, Cardolan, Rhudaur and Arthedain and declined in strength until it was destroyed in war with Angmar. In the Second Age Gondor was ruled cojointly by Elendil's …

…contacts declined for three centuries. Contacts were renewed by the royal marriage of 1940 TA but then terminated by the fall of Arthedain. There the matter ends until the Fourth Age and the return of the King. The Northern Realm is gradually restored and Elessar rules both Gondor and Arnor as High-King of the Reunited Kingdom, suggesting a single throne for both realms and a return to the close ties that existed under Elendil. (Warren Lawless 1996)