Growing up with a sister makes people more balanced
Growing up with a sister makes people more optimistic, more ambitious and better balanced, psychologists have found.
A study of 571 families comprised of brothers, sisters, a mixture of both and only children found that having a sister in the home led to siblings of either sex scoring more highly on a range of standard tests for good mental health.
They were found to be better at coping with setbacks, more highly motivated, had more friends and a better social life than those who grew up with just brothers.
The rest here.
(Thanks for the link, Becky!)