Paramessu acted as Horemheb's vizier as well as holding a number of military titles including that of Commander of the Fortress of Sile, an important stronghold on the land bridge connecting the Egyptian Delta with Syria-Palestine. The role assigned to Paramessu reveals Horemheb's preoccupation with the military situation in Egypt's northern territories.
Paramessu's family came from Avaris, the former capital of the Hyksos. It is significant to recall the role of its local god Seth during the Hyksos time. Horemheb also built a temple for Seth at Avaris, then the Ramesside Royal Family considered the god Seth to be their royal ancestor, and a fragment of an obelisk, recently discovered on the seabed off the coast of Alexandria, shows Sety I as a sphinx with the head of the Seth-animal offering to Re-Atum.
When Horemheb died childless, Paramessu succeeded him as Ramses I. With him, began the Nineteenth dynasty, although there is some evidence to suggest that the Ramesside pharaohs considered Horemheb as the true founder of the dynasty.
Ramses I must have been old when he ascended the throne, since his son and probably also his grandson had already been born before his accession. During his short one-year regency, and may be even before, his son Sety was appointed vizier and commander of Sile. Sety also held a number of priestly titles linking him with various gods worshipped in the Delta, including that of High Priest of Seth.