rulers
... that Mecklenburg underwent a series of partitions, so that by the 18th century, rulers in both of its parts had identical titles?
... that <a href="./Mecklenburg" id="mwEM8" rel="mw:WikiLink" title="Mecklenburg">Mecklenburg</a> underwent a series of partitions, so that by the 18th century, <b id="mwENA"><a class="mw-redirect" href="./List_of_Dukes_and_Grand_Dukes_of_Mecklenburg" id="mwENE" rel="mw:WikiLink" title="List of Dukes and Grand Dukes of Mecklenburg">rulers</a></b> in both of its parts had identical titles?