This volume provides a road map through the challenges of family diversity and family change in Western societies. Family forms, what it means to be a member of a family and the expectations people have of family relationships vary with time and space. As we will shortly see, today, marriage and family relationships are formed and maintained in an environment of greater choice in how women and men can live their lives than has been possible for past generations. Following Beck (1992), choices are made in a world that no longer has universal certainties, risks and fixed models of life.

Changing gender identities – gender identity may be defined as a person's inner sense of being a woman or a man, or another gender – have had a direct impact on the processes of family formation and models of motherhood and fatherhood in the Western experience. Obviously, gender identities and gender roles provide much of the organising structure in family life (Barnard and Martell, 1995; Parke, 1995), and, we would argue, changes in gender identities and in gender relations are at the root of family and social change (Demo et al, 2000; Hall, 2000; Erera, 2002; Sullivan, 2006; Klett-Davies, 2007; Gabb, 2008; Lamanna and Riedmann, 2009; Kapella et al, 2010; Woodward, 2011).

In particular, we notice a move towards more individualised and flexible decision-making processes, distant from the formal frameworks that used to shape women's and men's decisions in matters of relationships and family life. In fact, it is possible to identify many diverse family structures today, such as one-parent families, unmarried couples with children, Lesbian, Gay, Bisexual, Transsexual, Transgender, Intersex and Queer (LGBTTIQ) families, divorced families, reconstructed families, mixed families, couples where the two partners live in separated domiciles, and asexual and childfree couples (see, eg, Demo et al, 2000; Beck-Gernsheim, 2002; Baca Zinn et al, 2010).

These new living arrangements are the communes of the 21st century, the century inhabited by the Millennial generation (also ‘Digital’ or ‘Net’ generation). The Millennials are the newest generation, a group of young people whose birth years range from 1980 to 1982 onwards.