Cathy Elliott created several excellent Dundas web pages filled with details of Dundas family history. Here is one, listing most of the Dundas Cadet Branches. A cadet branch is a noble House that descends from another noble House. They are usually created when a younger member of a noble House, who is not the current heir of the family seat, is granted lands and titles of his own.
Additionally, a Sept is defined in Wikipedia as a division of a family, especially of a Scottish or Irish family. The term is used in both Scotland and Ireland, where it may be translated as sliocht, meaning "progeny" or "seed", which may indicate the descendants of a person. Several Septs evolved in County Fermanagh, Ireland. These Septs include the following branches: