Drillmasters and Legionary Captains.

[Marshal Murat]

Is there a way to auto add units to an heir?
With the Romans, I would like to have Drillmaster, Scout, Legionary Captain, and otherwise, because it was typical to have all these men attached to the person in command.

[Bob the Insane]

These extra guys arrive at random or by event on any general... Not just the faction leader or heir... Many of them can be aquired by putting your general in the right situation. Lots of fighting for the one's you listed...

Finally if a general has some followers you would like to see with your faction heir, then get the general and heir in the same place (same city or army) and then you can drag and drop the followers from one general to another...

Edit: To actually answer your question... No...