I think that this is generally true, but not in all cases.
Our family is definitely the most important group of people in our lives as we grow up. They give us our basic education -- both academic (to some extent) and social. They teach us lots of things that we need to know for school, but they also teach us how to behave.
Later in life, our families become less immediately important. They do not influence us as much on a day to day basis. So we can say they are no longer the most important people. However, they still have a huge impact on us because they have sort of created the foundation that has made us into the people we are. So even though they do not impact our decisions and such directly, the things they taught us early on continue to have a huge impact.