Narcissist and unconditional love
The Narcissist is in search of unconditional love. Means: The Narcissist is looking for the love of a person who satisfies his needs unconditionally. That's why he usually lives in symbioses. Either
a) with himself and a mirror or
b) with a Co-Narcissist, in which he continuously reflects.
You might think now that variant b) is less common, since the Co-Narcissist can not be perfect, of course, because the Narcissist himself is the best, always, undoubtedly and in every case.
But this is not like this. The Narcissist is quite capable of learning, if it turns out to be useful for his image. In this sense, the Co-Narcissist at the side of the Narcissist might be a thoroughly useful instrument in the overall social context.
Note: Marriage finally is nothing else but a status symbol! Thus the Narcissus decorates himself with the final touch of normality and seriousness. And: Even Narcissus has got a few needs besides his unique mission in this world. These do sometimes require personal relationships with other people. A spouse is once the bottom line and seen in the long run, even under the pragmatic criteria of cost-benefit accounting, the best of all existing real solutions.
An optimally functioning Co-Narcissist could be the ideal supplement to satisfy the needs of the Narcissist, if he finally learned to anticipate the wishes and whims of the Narcissist and wouldn't dare to contradict him. But that' exactly is the problem of the Co-Narcissist. Otherwise, the connection would be really perfect.
A life task
The Co-Narcissist usually is a faithful soul and finds his life's task in the Narcissist. In the truest sense of the word, because this task will certainly fulfill him for the whole rest of life. But this great dedication of the Co-Narcissist will be rewarded: The Narcissus confers a meaning to him (or her) that he (or she) never had until then. As a piece of the Narcissist’s ego-puzzle.
That, in turn, suits the Co-Narcissist very much. Therefore, it would simply be overdone to call the Narcissist an ordinarily parasite. Despite the fact he is quite self-interested. Because for a willing and docile partner, the relationship with a Narcissist surely has certain advantages. One could also say: These two sought and found each other. That can sometimes work out well and is, maybe, a kind of love, as well…