They are relationships in which love and rivalry – as well as envy and empathy – coexist, if not always easily. Sisters know each other inside out. They know better than anyone else each others hopes and dreams – and, as Amy proves, they also know precisely what to do and what to say in order to wound one another.

Why do we love our sisters?

Shes the first to give you a dose of tough love. Shes seen you at your worst and at your best, and she loves you anyway. Shes you go-to babysitter for your kids (or she will be when you have kids). It doesnt matter how far apart the two of you live, you know shes always with you.

Why are sisters so important?

Multiple studies have found that having a sister has a positive effect on all siblings. They bring something to families that brothers alone dont seem to, and make for happy children who grow into happy adults. In the long run, youre healthier and happier because of your sister.

Can a man marry his adopted sister?

It is a much better idea to never enter into a romantic relationship of any sort with an adopted sibling, even if this person came into your life later in childhood. The bottom line is that no siblings, whether by blood or adoption, can legally marry—nor should they.

How do sisters influence you?

Our research at the University of Calgary and the University of Toronto shows that siblings, like parents, can have a dramatic impact on one anothers development. And if one sibling is struggling to be empathic but has a sibling with strong empathy skills, they manage to become more empathic over time.