Perhaps within the last 100 years, but not "historically" in a general or broad sense. The historical ruling class didn't have professions, they had power.
Edit: If I may elaborate on this.
Also, i did not mean the political sense of "ruling class". I meant, strictly speaking, their status as economic agents. If you are a partner in a partnership, you have legal control rights. Same as if you are a material shareholder in a stock-company. You are not an "at-arms-lenght-employee" in other-words. So, the idea that you would need a union for what were in essence "company directors" just does not make logical sense. Again, that changes when (whatever the expertise) thes folks are forced to work for the state; they are then stripped of their control rights and take on a position more akin to Labour, structurally.
[1] http://en.wikipedia.org/wiki/Labor_unions_in_the_United_Stat...
[2] http://www.motherjones.com/politics/2012/03/what-are-right-t...