How do you define "family"?

I think that it is sad that social scientists have a hard time defining the family.  Growing up I always thought that a family had a mom, dad, and children.  According to the Family: A Proclamation to the World a family consists of a mom and dad who are married and have children.  The family is central to God's plan of happiness and this is how God intends families to be, but unfortunately the nuclear family is becoming less and less common.  What can be done to stop this trend? I think one way would be to encourage people to marry first. A family starts between a man and a woman and if they get married and are committed to each other than they can provide a good home for future children.