This book describes a new way of being a couple and a new family form—living apart together—where couples who are committed to one another nevertheless maintain separate residences and finances. Although studied previously in Europe and other areas, LAT has not attracted attention in the United States, although it appears to be as prevalent there as elsewhere. After presenting the research done about LATs in other areas of the world, the book presents the results of the author’s empirical research on this lifestyle—both the results of surveys taken in 2016 and of interviews of LAT couples in 2016 and 2017 in the United States and England, which explore the numbers of LATs, their reasons for living apart, their demographics, the economics of their relationships, and their mutual caregiving. It also compares and contrasts this lifestyle with both commuter marriage and cohabitation. A particular focus is placed on the special role that LAT appears to play in the lives of women, gay males, and couples 65 and older. Ways in which LATs encounter the US legal system currently—primarily with respect to the termination of alimony upon cohabitation—are described and criticized. After discussing what the purposes of family law should be in general, the author proposes a number of legal reforms that should be undertaken to support the caregiving functions LAT partners perform for each other.