This is a tough one.  My generation,  born in the Depression,  learned to define 'family' as what is now called the nuclear family:   father the breadwinner, mother the homemaker and 2.1 children.  In an episode of the Murphy Brown television series (1988 - 1998) a position was taken  that love is what defines families, rather than a rigid pattern intended for procreation.  A couple of decades ago the  Family Law Reform Act of Canada made alterations in the definition of family and its components so as to eliminate ___ in law -  the concepts of common-law marriage  and illegitimacy. More recently same-sex marriages became legal in many Canadian jurisdictions. What some saw in these legal changes as  erosion of family (the nuclear family of course) I saw as legal recognition that there is more than one way to be a family, and more than one way to be a parent.

I am interested in documenting families.   One way to do this is to develop family trees, and  for this I use a computer program.  There are many versions of genealogical software;  I use one appropriately called Brother's Keeper.   Brother's Keeper (or any other such program) allows the user to put together the skeleton of a family - the names, the dates, the relationships.  The bones need to be fleshed out , and that happens with the recording and making accessible of family stories, anecdotes, and  memorabilia and as well formal documents like birth, marriage and death records, census records, church records, cemetery records and a wide range   of other sources.  Since the day I first asked the question, "How many first cousins do I have?"  this is what I have been doing for my family lines and for  those of my husband, so as to provide as much information as possible about their forebears for our descendants.

Defining family becomes important when decisions need to be made about how people outside the old nuclear family concept will be documented.  This became clear to me recently, in reading the obituary of an uncle.  The obituary stated that he had three sons, and indeed he did, but none of them were his sons by birth: one was adopted and the others  fostered.  But for them to be defined as his sons, his FAMILY, in the obituary meant that the old definition was irrelevant.  I co-opted not only the foster sons as my first cousins, but also their spouses, and so I acquired connections to many more families.  MY family is inclusive, not exclusive.  MY family includes anyone who FEELS like family.

This presents a difficulty when it comes to entering some of the people who feel like my family in the Brother's Keeper data base.  What about a friend who feels like a brother?  I would like to include him and his family, but that would mean giving my parents - or my husband's - a son they didn't know they had.  So this friend, as close as any brother, must,  due to the limitations of the software, remain outside my family tree.  

Another  difficulty:  the software doesn't allow for same-sex marriage and insists that married couples be of different genders.  For my beloved cousin who  legally married his partner, I cannot document them as spouses unless I change the gender of one of them.  The world has moved on, and the genealogy software has not kept up.

Googling "Definition of Family" produces remarkable collections of words, several millions of them.  At the top of the first screen, this:  A family is a social unit living together.  This definition doesn't identify the composition of the social unit, but limits itself to stating that the  component parts live together.

My family lives all over the world,  however, so this definition doesn't work for me.  While most of the components of my family are connected to me by blood or marriage, many are neither, and yet they are my family.   Millions of definitions do not alter what I FEEL my family to be.  I may feel greater or less kinship with one member or another, but regardless, they are my family.   I feel as close to a half first cousin once removed as I do to my blood sister, and as close to a fourth cousin as I do to my brothers.

The example of the three sons of my uncle - all of whom I regard as my cousins - places my personal definition  in personal terms:  my family is who I say my family is.