“You can choose your friends, but you can’t choose your family.” That line comes from American writer Harper Lee’s book “To Kill a Mockingbird.” Now compare her words to another famous expression: Blood is thicker than water. This means that family will always be with you while other people -- with no blood connection -- may come and go. Having strong ties to family and friends has long been identified as an important part of being happy and healthy. People need people. However, if forced to choose which is more important, American researchers now say friendship is more important than family. Their new study suggests that friends may be more important than family members, especially as we age.