For the first time, researchers have shown that the pre-hatching calls of baby Nile crocodiles actually mean something to their siblings and to their mothers.

The Nazca booby, a Galápagos Island seabird, emerges from its shell ready to kill its brother or sister. Wake Forest University biologists and their colleagues have linked the murderous behavior to high levels of testosterone and other male hormones found in the hatchlings.

German researchers have found that heart disease of the left main coronary artery is often an inherited condition that clusters in families. Moreover, they discovered that initially healthy siblings of a person with the condition were 2.5 times more likely to go on to develop some form of heart disease than were siblings of a patient with heart disease that did not relate to the left main coronary artery.

Children with older delinquent siblings are at high risk for becoming juvenile delinquents themselves. Researchers have been studying family interventions that prevent young high-risk children from following in the footsteps of their older siblings.

Children who have older brothers become more aggressive over time, on average, than those who have older sisters. Older siblings with younger sisters become less aggressive.

The next time you venture into your garden armed with plants, consider who you place next to whom. It turns out that the docile garden plant isn't as passive as widely assumed, at least not with strangers. Researchers at McMaster University have found that plants get fiercely competitive when forced to share their pot with strangers of the same species, but they're accommodating when potted with their siblings.

When parents treat their children differently, siblings and parents often have very different ideas about what's happening and why, says a University of Illinois study. And there can be as many points of view as there are family members.

Children whose parents were trained in mediation skills had better conflict-resolution skills than those whose parents did not receive training. That's the finding of a new study conducted by researchers at the University of Waterloo in Ontario and published in the May/June 2007 issue of the journal Child Development.

Younger siblings of children with autism are at risk to suffer from delayed verbal, cognitive and motor development in their early childhood years.