I belong to a family of four, with my two parents and a younger brother. We all get along very well and I definitely enjoy being with them very much. While I admit it would be better if I had good friends as part of my life as well, especially during times when I'm not with my family, I am not really keen on making friends. I am thankful for my family and feel that they are good enough to keep me happy and prevent me from being lonely. Thus, I feel that friends may not really be necessary.
No, it is not good enough to have a family but no friends, because close friends are like family. We live in a community, and the community is critical to functioning in the world. We can't depend on family alone. Friends needs to help each other and challenge each other, in order to make the world work in the best way possible.