4. A corresponding displacement of incestuous desires, leading to a similar repression and reversal of emotion, may occur in the case of the mother-in-law herself, who, in virtue of this displacement, identifies her son-in-law with a son of her own (either real or imaginary); the one re-awakening in her incestuous tendencies originally aroused in connection with the other. Or again, the primary motive on the part of the mother-in-law may be unconscious sexual jealousy of her daughter, to whom she grudges the superior attractiveness of youth and the pleasures of dawning sexual life--a life which for the mother may be largely or entirely at an end. In this case she may unconsciously identify herself with her daughter, imagining, as it were, that it is she herself, and not her daughter, that is married to her son-in-law. In either case it is often the less tender and more sadistic elements of the mother-in-law's love which are directed to the son-in-law, since these are more easily reconciled with the maintenance of the requisite degree of repression than would be the case with the more gentle and affectionate components.
Only less important than the relations of child-in-law and parent-in-law are those of step-child and step-parent[111]; and such lesser degree of importance as these have is due rather to the lesser frequency of their occurrence than to any lesser significance which they possess for the individuals actually concerned. The generally outstanding feature of these relations is the manifestation of a more intense, or at any rate a more open, form of those feelings and tendencies which would normally exist between the child and the corresponding blood parent. A boy, for instance, who may successfully have displaced or repressed his original feelings of jealousy or hostility towards his own father, may often prove incapable of carrying out a similar re-adjustment in the case of a subsequently acquired step-father. The latter may have none of the glamour which belonged to the former in virtue of his position as head of the family (and therefore centre of the child's world) during the infancy of the child (_cp._ p. 55) and which may have helped to inhibit the original hostility experienced towards him through arousal of the opposite emotions of love, gratitude or admiration. The step-father, therefore, may easily re-awaken in his step-son any remnants of the hatred which the latter may have experienced towards his real father, without re-awakening in corresponding degree the compensating forces which kept the hate in check.