Personally I try not to deal with such people at the level of familial relationship. The best armour is not to be there when the attack it made and all that. In business then the self serving nature of such people means you will encounter them, sometimes they are good at what they do and sometimes they are an example of politics or the peter principle (everybody rises to the level of their incompetence).
Depending upon your age, income, family status (will cutting them out necessarily cut out others* you would rather be in contact with sort of thing) and more that may be harder to pull off.
*not necessarily because they forbid it but others are in their orbit and dislike you pulling away. Throwing around the word cult is a bit premature at this point but there is a reason most such things are headed by such.
It also depends upon you yourself. What skills you have, what your mindset it like.
For instance I am a cold and clinical bastard that has never felt lonely, and is happy to analyse every single move at all points with an almost perfect memory for conversations and interpersonal interactions. Quite easy then to figure out if someone is self serving to the degree of some kind of clinical narcissism and then whether their actions and responses work for my cost-benefit, even if they either collapse it to their benefit or run away when the going gets tough leaving me to shoulder burdens they should have had.
You may however not have such perks (or be able to gain them -- people think in different ways and trying to change your thinking radically is dubious at best), and even if you did your cost-benefit risk analysis will necessarily be different ($500 might be a cost of doing business for me, crippling for you to lose).
That said if you seek validation through them then don't. If you get it then it will likely still be self serving, if not meaningless, so eh.
Do be sure it is actually the case as well; children rebel against their parents, I would say it is actually an essential aspect of growing up. Leading by example, reinforcing social standing when you do something to damage it... such things can appear as narcissism to those not necessarily familiar with it.