Over the course of the last few decades, the nature of close personal relationships has evolved dramatically. More and more people choose to marry in their 30s and 40s, meaning that an unprecedented number of people start families later in life than ever. Around the world, more cultures are embracing nontraditional lifestyles, ranging from cohabitation prior to marriage to polyamory. Many regions have grown more accepting of diverse gender and sexual orientations, and as a result, the image of what a family is, who has one, and at what age it is acceptable to start one all look very different from previous generations. Even our friendships have evolved, with technology bridging physical and interpersonal distances in previously impossible ways. This volume compiles the latest research and theory on close relationships in the twenty-first century from multi-disciplinary and international perspectives with the intent of taking stock of the cultural, political, and legal changes that have shaped the relationship landscape. Some of the important shifts that are captured are the rise of singlehood, online dating, and cohabitation, the new importance of social media, marriage equality, and changes in gender norms. New ways of forming families and unions via adoption, assisted reproduction, and remarriage are also covered, as well as coupling across cultural, racial, religious, and national lines.Knitting together a diverse pool of international expertise, this book synthesizes a truly modern take on close personal relationships in the twenty-first century.