I definitely agree that siblings can be heavily influential on each others actions. However, that being said, I don't know how this study can separate the fact that sibling pairs have shared life experiences, and thus, the fact that sibling pairs are more likely to undergo a particular behavior could simply be a result of those shared life experiences, and not necessarily a younger sibling emulating an older sibling...
"In the aftermath of the bombings in Boston many of us have been thinking a lot about siblings — particularly how older siblings can shape the lives of younger siblings. But until pretty recently, the role siblings play in determining the trajectory of each other's lives hasn't been a particularly hot topic in psychological research. Psychologists, very understandably, have focused on the influences they see as more important — such as parents and peers and genetics.
But in the past decade that's been changing a bit. Psychologists interested in how siblings affect one another are taking a new look at all kinds of behavior, particularly anti-social behavior."