For those students with younger siblings, the study found, their success in turn has a positive influence on those siblings once they reach middle school — particularly among children from disadvantaged families. For younger siblings, having an older sibling born shortly after the kindergarten cutoff was associated with an increase in total math and reading scores during middle school, according to the study. The study’s findings suggest that children in disadvantaged families may be more likely to view their older siblings as role models, she said, adding that the older sibling’s influence can be positive or negative depending on the situation.