The sibling-rivalry model suggests that aggression between siblings reflects jealousy and nonrealistic conflict. A realistic conflict model, on the other hand, suggests that sibling conflicts arise over tangible goods and the performance of disvalued tasks because proprietary rights and the division of labor within the household are often unclear. These conflicts are likely to become overt if intervention from parents is anticipated because then younger siblings are willing to fight their more powerful older siblings. This suggests that siblings fight less when parents take a laissez-faire approach because the younger sibling is forced to submit. These models were tested through a questionnaire distributed to 309 college students in three large introductory sociology classes. Only students who had at least one sibling were asked to complete the questionnaire. Students were asked to think about when they were in junior high school and to answer a series of questions about the sibling nearest them in age. The questions measured various variables related to the models designed to explain sibling aggression and violence. The data support the realistic conflict model but not the sibling rivalry model. 7 tables and 32 references. (Author abstract modified)