So it all started, officially according to the Danish Nobility Yearbook, with Johan Rantzau married to Abel Breide.
He should have sired 10 sons, but only 7 are mentioned, and most of these are educated guesses. Of only 3 of his sons it is known they had offspring, viz. Cai, also named Gotskalk, and Volmer, also called Breide.
Most likely they were halfbrothers. Another son Otto had no grandsons.
However, Cai is most likely named after his grandfather, and hé was most likely married to a Christine named in 1326. If we follow this reasoning, the other Johan named in 1226 must be the great-grandfather of Cai.
Cai and Breide must then be the equivalents of the Schack and Breide who are mentioned earlier, as only these two can cover all Rantzau's. This is visualized in the Excel diagram, which begins with Cai and Christine.
Beside the branch which eventually leads to the present Danish Rantzaus, there were originally three German branches.
One split up early in the Dutch and the "German I" branch; the Schmoel branches. The 2nd into "German II" and III.
The third original branch only split up as shown in "German IV". These six branches are , with more detail, available as Excel diagrams. They are also given as text files, but only for the last 6/7 generations. These can be accessed from the previous page. See the Exel diagram for an overview combining those three branches. If you have EXCEL, that is!.
Not all "von" Rantzau's belong to the same branch! Neither do the "zu" Rantzau's!
A brother to the first named Danish count sired the first bastard, Jens Pedersen Ørsted.