Over the Middle Ages, genealogy became increasingly important, as you say, for inheritances and to avoid consanguinity in high-profile marriages. Consanguinity meant that a Christian could not marry anyone within seven degrees of family relation, the equivalent to a sixth cousin, and great effort was often put into avoiding defying the wishes of the Church in this matter. It is not then surprising that by the late twelfth and eleventh century, there was increased interest in constructing genealogies. The Synod of Ingelheim, 948, urged all Christians to make a list of their ancestors for the purpose of consanguinity. In the twelfth century, Ivo of Chartres was able to announce that a proposed marriage was forbidden, as a written genealogy had been brought before him.

A powerful noble family would often be patrons or founders of monasteries. One of the past-times of monks was the writing of history, which was seen as a way of reflecting on the divine touch in human affairs. More generally, Greary has argued that monasteries had the institutional continuity often lacking in the age necessary to maintain records. The Chronicle of the Counts of Anjou, written c. 1100 by Angevin monks, for example, narrates the history of the family beginning from Tertullus (d. 887), "reckoned by the ancient genealogies" to be the founder of the dynasty who may be semi-mythical. A Burgundian chronicler of the twelfth century, when giving genealogical information, states that he knows this as the names appear frequently in the monasteries' charters where family members would frequently be listed. Nobles could also commission pieces of arts showing family trees, like this one for the German Salian dynasty, and here is one, slightly earlier, of the dukes of Normandy down to Richard I (933-996). On the visually larger scale, towns may be decorated with statues and churches with tombs of one's noble ancestors. Here is an effigy of the first Duke of Normandy, Rollo. In addition to monastic work and art, as the increase of nobles' household officials grew and the nobility itself became more established, it was more likely that this kind of genealogical investigation would be done within the noble household itself.

Often, however, primary sources such as chroniclers are unclear on exact family relationships for younger sons and daughters, making the construction of family trees at present more difficult. Genealogies were rarely intended to be complete in the sense of including every single individual within the family: the names of eldest sons and heirs, and perhaps those daughters for whom notable marriages were made, would have been more readily available in the sources that a medieval genealogist would use.