What's the secret to happiness? According to a study by the University of Ulster, the answer is: having sisters!
Lead researcher Professor Tony Cassidy said: "Sisters appear to encourage more open communication and cohesion in families.
"However, brothers seemed to have the alternative effect. Emotional expression is fundamental to good psychological health and having sisters promotes this in families."
He said many of the participants had been brought up in families where parents had split and the impact of sisters was even more marked in these circumstances.
"I think these findings could be used by people offering support to families and children during distressing times. We may have to think carefully about the way we deal with families with lots of boys."