Amenemhat I
Amenemhat I is considered to be the first king of Egypt to have had a coregency with his son, Senusret I. A double dated stele from Abydos and now in the Cairo Museum (CG 20516) is dated to the Year 30 of Amenemhat I and to the Year 10 of Senusret I, which establishes that Senusret was made co-regent in Amenemhat's Year 20.