Pruett studied seventeen two-parent families of firstborn children whose fathers bore primary responsibility for caretaking. The infants proved to be vigorous and competent, without apparent gender identity disturbance, and their fathers capable of intensely nurturing, reciprocal attachments. The fathers' caretaking styles reflected their selective identifications with their parents and spouses and their needs to nurture and be nurtured. The infants showed heightened appetite for novel stimuli, possibly as a consequence of fathers' more active styles, and possibly due to the heightened libidinal commitment of two parents. The author challenges the usual theoretical distinction between primary and secondary love objects and suggests that the infants thrived in consequence of their integration of distinct and more balanced parental attachments and their stimulus-rich experiences of mutual regulation.