The quality and stability of sibling relationships during adulthood were assessed by comparing Thematic Apperception Test (TAT) themes of sibling affiliation, conflict, and separation at the periods of active child-rearing (CP) and the empty nest (EN). Thirty men and 30 women, equally divided between the two life stages, were randomly selected within a designated neighborhood from a pool of married people with a same-sex sibling within 3 years of their age. The relationship with this sibling was targeted because it is usually a highly charged one, both positively and negatively. A projective instrument, the Sibling Thematic Apperception Test, was used to elicit underlying feelings about the relationship, because traditional methods of assessment have failed to tap the negative qualities of sibling relationships. Results showed no differences in affiliation theme frequencies for the CP and EN men and women contrary to previous findings. Separation themes, however, were more frequent for CP than for EN men and women, suggesting that the desire to separate from siblings reflects a developmental process related to bonding with the family of procreation. Although there were no sex differences within life periods, stories about sisters had more conflict themes than stories about brothers, an unusual finding which might be attributed to the use of an in-depth approach. (A seven-page list of references and three data tables are appended.) (Author)