lstoy, in The Kreutzer Sonata, has said all that we suspect about it.
When it persists beyond the period at which it ceases to be necessary to
the child's welfare, it is apt to be morbid; and we are probably wrong
to inculcate its deliberate cultivation. The natural course is for
the parents and children to cast off the specific parental and filial
relation when they are no longer necessary to one another. The
child does this readily enough to form fresh ties, closer and more
fascinating. Parents are not always excluded from such compensations:
it happens sometimes that when the children go out at the door the lover
comes in at the window. Indeed it happens now oftener than it used to,
because people remain much longer in the sexual arena. The cultivated
Jewess no longer cuts off her hair at her marriage. The British matron
has discarded her cap and her conscientious ugliness; and a bishop's
wife at fifty has more of the air of a _femme galante_ than an actress
had at thirty-five in her grandmother's time. But as people marry later,
the facts of age and time still inexorably condemn most parents to
comparative solitude when their children marry. This may be a privation
and may be a relief: probably in healthy circumstances it is no worse
than a salutary change of habit; but even at that it is, for the moment
at least, a wrench. For though parents and children sometimes dislike
one another, there is an experience of succor and a habit of dependence
and expectation formed in infancy which naturally attaches a child to
its parent or to its nurse (a foster parent) in a quite peculiar way.
A benefit to the child may be a burden to the parent; but people become
attached to their burdens sometimes more than the burdens are attached
to them; and to "suffer little children" has become an affectionate
impulse deep in our nature.

Now there is no such impulse to suffer our sisters and brothers,
our aunts and uncles, much less our cousins. If we could choose our
relatives, we might, by selecting congenial ones, mitigate the repulsive
effect of the obligation to like them and to admit them to our intimacy.
But to have a person imposed on us as a brother merely because he
happens to have the same parents is unbearable when, as may easily
happen, he is the sort of person we should carefully avoid if he were
anyone else's brother. All Europe (except Scotland, which has clans
instead of families) draws the line at second cousins. Protest