After 1261 the previously jointly ruling brothers Gerhard I and the elder John I divided the Counties of Holstein and Schauenburg (Schaumburg). Gerhard I received the Counties of Holstein-Itzehoe and Schaumburg, whereas John received the County of Holstein-Kiel. After the death of John I, his sons Adolphus V and John II reigned jointly in Holstein-Kiel. In 1273 they partitioned Holstein-Kiel and John II continued ruling over Kiel; Adolphus V the Pomeranian then received Segeberg (aka County of Stormarn). Adolphus V was succeeded by his nephew Adolphus VII. Lacking a male successor upon the death of Adolphus VII in 1315, Holstein-Segeberg was reincorporated into Holstein-Kiel.
After the death of Gerhard II his sons Gerhard IV and his younger half-brother John III the Mild inherited and ruled in Holstein-Plön together. In 1316 the brothers militarily seized the possessions of John II the One-Eyed (d. 1321) in Holstein-Kiel, whose sons had been killed. John III the Mild, before a second-born co-ruling count in Plön, then received Kiel from the deposed John II the One-Eyed, a cousin of his father Gerhard II the Blind. Gerhard IV continued ruling Holstein-Plön as sole count.
Till 1381/84 joint rule of the brothers Henry II the Iron, and Nicholas (Claus), both also Dukes of Schleswig starting from 1375; after Henry's death Nicholas ruled jointly with his nephews Albert II and Gerhard VI. In 1386, Nicholas resigned as Duke of Schleswig and Gerhard VI succeeded as Duke Gerhard II (1386–1404).
Holstein-Rendsburg gained Kiel (incl. Plön) by inheritance in 1390.
Holstein partition of 1397 and the extinction of the Rendsburg line in 1459
In 1390 the Holstein-Rendsburg line had assembled the larger part of the partitioned Holstein counties, to wit Kiel, Plön and Segeberg, but not Holstein-Pinneberg, which existed until 1640. Members of the Rendsburg family branch were often also simply titled as Counts of Holstein after 1390. For the Pinneberg family branch, usually residing in the County of Schaumburg, the titling after Schaumburg started to prevail.
In 1397 after the death of their uncle Nicholas (Claus), with whom the nephews Albert II and the elder Gerhard VI had jointly ruled Holstein-Rendsburg, they partitioned Holstein-Segeberg (aka county of Stormarn) from Holstein-Rendsburg, with Albert receiving the new branch county in return for waiving his co-rule in Rendsburg. After Albert's death in 1403 Segeberg reverted to Rendsberg. In 1459, with the death of Adolphus XI (aka VIII), the Rendsburg branch was extinct in the male line and the nobility of Holstein-Rendburg and of Schleswig then assigned the succession to his sister's son King Christian I of Denmark, House of Oldenburg.
Henry IV, also Duke of Schleswig as Henry III (1404–1427)
Seals of Adolphus ↑ and Gerhard ↓
Till 1433 joint rule by the brothers Adolphus XI (aka VIII) as Adolphus I and Gerhard VII as Gerhard III simultaneously claiming dukedom in Schleswig, with Adolphus gaining royal Danish recognition in 1440
With Adolphus' death the Rendsburg line was extinct, his nephew Christian I of Denmark, House of Oldenburg, inherited the County of Holstein-Rendsburg, elevated to the Duchy of Holstein in 1474.
The last Schauenburg line ruling Schaumburg and Holstein-Pinneberg till 1640
After King Christian I of Denmark, House of Oldenburg had been chosen as heir to the County of Holstein-Rendsburg Christian ascended to the comital throne in 1460. In 1474 Frederick III, Holy Roman Emperor, elevated Christian I from Count of Holstein-Rendsburg to Duke of Holstein. For his succession in the Duchy of Holstein see List of rulers of Schleswig-Holstein#House of Oldenburg (1460–1544). The Schauenburg line in the Counties of Holstein-Pinneberg and Schaumburg persisted until its extinction in the male line in 1640. This line is also known as Holstein-Schauenburg. The Counts were elevated to Princes of Schaumburg in 1619/1620, however, the Dukes of Holstein opposed the transition of that title to the County of Holstein-Pinneberg.