The 870 treaty which divided the territory between the east and west Frankish kingdoms provides the best starting point for identifying the counties which developed within the kingdom of Lotharingia.
Assignment of counts to these counties was in many cases of short duration, with many changes and exchanges of territories (including between the Lower and Upper Lotharingian duchies) which renders satisfactory reconstruction of the comital families extremely challenging.
What is clear is that a finite group of local higher nobility enjoyed power in both Upper and Lower Lotharingia, linked by family relationships many of which will never be confirmed precisely because of insufficient information in surviving primary sources.
After the deposition of King Charles III in 923, German influence in the territory of Lotharingia predominated.
According to Thietmar of Merseburg, Heinrich I King of Germany secured the release of King Charles from prison and in return was rewarded with "the right hand of St Denis and the entire kingdom of the Lotharingians"The duchies of Upper and Lower Lotharingia were created in 959 in response to local rebellions and in order to assert greater local control from Germany.
Onomastics is of some use in identifying possible connections, but the number of permutations through both male and female lines is generally too numerous to render precise identification anything other than speculative.
This difficulty is increased because of the changes in comital assignments which make it impossible to assess with any accuracy the extent to which appointments were hereditary within the same families.
The newly created kingdom covered a wide strip of land which stretched from the North Sea coast southwards to Italy, and included present-day Belgium, Luxembourg, The Netherlands, Germany west of the river Rhine, the French provinces of Alsace, Lorraine, Burgundy and Provence, Switzerland and parts of northern Italy, as well as the imperial cities of Aachen, Pavia and Rome.
The kingdom was divided between the sons of Emperor Lothaire after he abdicated in 855, the territory called Lotharingia then being restricted to present-day Belgium, Luxembourg, The Netherlands, Germany west of the Rhine, the French provinces of Alsace, Lorraine, and Switzerland.
Lotharingia was an entirely artificial political creation and its name an artificial composition.