People who treat those closest to them with contempt but at the same tym show concern for new people

I have noticed this peculiar behaviour. Certain individuals do not appreciate people who are close to them, their subordinates, colleagues, wife, children etc. The more closely the individual is interacting with a person over a period of time, the more he will lose concern for the person. He will treat them with a sense of contempt. But at the same time such an individual will normally be really interested in interacting with new people, for whom they have a keen interest...even though it may be short-lived. But if that new person stays with the individual long enough most probably he too will be treated with contempt. So my question is ...what is the underlying cause of this behaviour which I feel is very detrimental for the emotional well being of the individual.