I agree with your diagnosis (I've already stated as much) with one exception. This is not really related to being an only child. Iwas one and I do not stalk people. And I worked with someone who had most of the "me, me, me" symptoms of being convinced everything belongs to him/her but was still on the sane side (barely). This person was a spoiled younger sibling. Sometimes it can be much worse than being an only child.