All Rees families in the world are actually related to one another. This bold statement can be made if one retraces the emergence of this surname. Hermann Terlinden, the former city archivist in the city of Rees, followed from his investigations that the surname Rees actually originated in the city of Rees. The klevian writer Egbert Hopp believes, that the city of Rees got its name from a courtyard of Rees or the nobles of Rees.

Already in the oldest charter of the monastery Rees (1079-1089) a man named Rees is mentioned, as "villicus Adelbrat" (estate steward). Between 1138 and 1143 a Cunradus Villicus de Reesa appears. Later Reinald Rees is often mentioned. The first name Reinald was kept over centuries by the Masters of Rees, which is considered as proof that they originated from a kinship.

Later the "Rees" are usually refered to as "Knights of Rees". In a document of the Rees city archives a donation from Bernhard von Rees to the Cologne archbishop is reported. A knight Johann von Rees was minister in 1298. At the same time also a judge of Rees is mentioned, known is also a Leo von Rees, canon at the monastery church.

The family van Rees showed itself as very vital, particularly in their Netherlands branches. In Antwerp, Amsterdam, Bruegge and Gent, the Rees brought it to prosperity and reputation as businessmen, merchants, bankers and also in the military service.

The court at Rees was in possession of a line of the Rees kin for a long time. A Johann von Rees was elected mayor of the city of Rees eight times between 1572 and 1584.

As coats of arms the nobles of Rees held a sign with a crossing in the right upper quadrant. In the Rees city archives illustrations of different coats of arms held by the Rees are present.

When sending the invitations to the "Rees Festival '73", organized by the city of Rees, it became clear that most families Rees, and van Rees can be found in the Federal Republic of Germany (there particularly in Baden-Württemberg), the Netherlands and in Wales/England. American families Rees agreed in that their ancestors had emigrated from Wales.

However, today there are Rees families also in Switzerland and in Sweden, in France, Belgium and Greece, in Canada and in Poland.