It's very common for relationships between superiors-subordinates to be banned or to have very specific steps which must be taken. Of course, for a superior to be 'making out' with someone at an event is potentially a whole different thing.
A subordinate in the context of a business org structure means someone who reports up into him, whether directly or indirectly. If the person reports up into someone who is his peer, say, the VP of Finance or VP of Marketing, then you would not refer to the person as his subordinate. And, in most (US) companies, a relationship between him and such a person in a different section of the company would not be considered problematic or against policy.