There has always been a distinction between the way people treat people with whom they have blood ties and those with whom they don't. It is believed that members of the same family should share certain benefits within the family only.
I would like to talk about family from another perspective. Family to me is a group of individuals who work together for the mutual benefit of every member of the group. Every member of the family works for the growth and edification of individual members.
To me, a family does not necessarily have to be a group of people with blood relations. It could be a group of tight friends, a professional association, a church group, a group of students and so on.
It is important to note that mutual help and benefit is sometimes not accessible even from blood relations. There are simply people who claim to be family who do not care about our progress or even our troubles. There's always the ones who don't care and the ones who are simply selfish.
To genuinely refer to someone as family, the person must be someone who understands you, who has personal plans as well as group plans that includes you. The person must be someone you can also refer to as a friend in the real sense of the word. The person must be someone who is willing to make sacrifices for you and for whom you can do the same. The person must also be someone who you respect and who respects you back. Age is not a determining factor here.
Take a look around you. There are family members who you can't exactly say you are friends with. Yet, there are friends with whom you share so much that they are worth much more to you than your family members.
Take time to sieve out people who you know are always present and are actively trying to make positive impact on your life. Those are the people you can call family, they are the ones you can look up to for help when things go south. They are the ones you can count on to be there for you whether things go wrong or right. They are the ones you know you can always rely on for discreet advice even about extremely private matters.
Family members should be kept close and their goodness should be reciprocated. Remember, to refer so someone as genuine family the person also has to be a genuine friend. Blood relationship is not the only criteria to select family.