Mieszko I of Poland one version of the legend of St. Wojciech it is written that Mieszko I had his daughter married to a Pomeranian prince, who previously voluntarily "was washed with the holy water of the baptism" in Poland. The above information, as well as the fact that Bolesław lost Western Pomerania, suggest that the region was not truly incorporated into the Polish state, but only became a fief. This conjecture seems to be confirmed in the introduction of the first volume of the chronicles of Gallus Anonymus concerning the Pomeranians: "Although often the leaders of the forces defeated by the Polish duke
Mieszko Kazimierzowic "Gesta principum Polonorum" written in the early 12th century, put Mieszko third in order, among his brother. Modern historian, Janusz Bieniak, has supposed that Mieszko was the second son of Casimir I and was older than Władysław Herman, but most scholars disagree with this hypothesis. The date of Mieszko's birth was given by "Rocznik krakowski" (Kraków Annals). This source omitted dates of birth of Mieszko's brothers. Kazimierz Jasiński thought that "Rocznik" was started shortly before Mieszko's birth and this was the reason for absence of his older brothers. Przemysław Wiszewski supposed tha Casimir I chose Mieszko as his successor and