After three years at the company, there is a hope that no one can literally or figuratively take your place, at least until the owner's son arrived. Although it is tempting to suggest that you arrive at work earlier and let him grab someone else's place, that is not fair to you, nor to the rightful user of the spot he would grab.
This single act by the son tells you a great deal about his attitudes, maturity, and level of awareness. If this is how he acts in the parking lot, one can only cringe at the thought of his behavior in the building.
You should consider going to your manager, to the son's manager, or to whoever assigns parking for the company and ask any of them for their help in correcting it.
You probably have good reasons for not wanting to approach the owner, but the fact that you have them indicates that this is not the most open and supportive workplace on the block. One key question is whether the son's arrival is a temporary stop, or if this is the beginning of a new era. The more you know about this, the easier it will be for you to determine how much longer you want to park your career here.
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