Research of the oldest aristocratic clans in Hungary encounters several difficulties. Sources of the period until as late as the 12th century usually noted only names of nobles without any mention of their family affiliation, nor any other genealogical relation, such as father or grandfather. Therefore, genealogical trees of most Hungarian aristocratic families can be put together only from the 13th century. However, there are some exceptions, such as the Hont-Poznans, an exceptional family that is written into the early medieval history of Hungary.