The past decade has witnessed dramatic changes in public attitudes about and legal status for same-sex couples who wish to marry. These changes demonstrate that the legal conception of the family is no longer limited to traditional marriage. They also raise the possibility that other relationships—cohabiting couples and their children, voluntary kin groups, multigenerational groups, and polygamists—might gain legal recognition as families. This Article probes the challenges faced by aspiring families and the means by which they could attain their goal. It builds on the premise that the state remains committed to social-welfare criteria for granting family status, recognizing as families only those categories of relationships that embody a long-term commitment to mutual care and interdependence and, on that basis, function well to satisfy members’ dependency needs. Groups aspiring to legal recognition as families must overcome substantial uncertainties as to whether they meet these criteria if they are to obtain the rights and obligations of legally recognized families. Uncertainty contributes to a lack of confidence in the durability and effectiveness of their relationships on the part of the aspiring family members themselves, the larger social community, and, ultimately, the state. The Article develops an informal model to illustrate the nature of these uncertainties, as well as the solutions to the possible obstacles they create. Using a hypothetical group consisting of two adult men and two adult women in a poly- amorous relationship, we show how legal status for family groups can result from an evolutionary process for overcoming uncertainties that uses collaborative techniques to build trust and confidence. Collaborative processes have been shown in other settings to be effective mechanisms for creating trust incrementally and thus appear to offer a way forward for novel families. The Article describes how the successful movement to achieve marriage rights for LGBT couples has roughly conformed to the collaborative processes we propose, and it identifies the absence of meaningful collaboration as one factor explaining the stasis that characterizes the status of unmarried cohabitants. This evidence supports the prediction that the future progress of other aspiring family groups toward attaining legal status may depend on how well they are able to engage the collaborative mechanisms that smooth the path from contract to status.