Family is more than just a biological connection. It's love and friendship, it's being there when you are needed… and sometimes when the other person doesn't even realize how much they need your comfort and support.
There's the nuclear family, the one you are born into, usually parents and children. Sometimes you are born into the hearts of your parents (adoption). When you are little, this family seems to be your whole world. If you are lucky there are aunts and uncles, cousins, maybe grandparents… As you grow your family takes on other forms, a marriage, your own children, in-laws, and sometimes close friends.
So how do you cope when the people you count on to be there for you as family turn their backs? How far do you push when the other person has no interest in BEING family? It's never easy to close the door on someone you called family, sometimes though they leave you no other options.
I have friends who have been abandoned by those they thought would be there for them in times of turmoil and it's sad. They've told me stories of being excluded from these people's lives and sometimes even getting arguments because they didn't acknowledge an event that they were never even told about.
Sometimes a person whom you accepted as family (maybe they married in) and continued to think of them that way even after the actual blood connection has been lost, may feel the need to "divorce" themselves from that side of the family. It's heartbreaking to lose yet another family member, but there is really nothing you can do about it.
Cling to those who hold you dear and don't waste time on those who seem to have simply forgotten you. Focus on the people who surround you with love and caring, and who allow you in when they need some love and caring as well. THAT is your family.