Drawing on examples of legal reasoning by the Law Commission for England and Wales, the American Law Institute and the Norwegian Supreme Court, this article argues that the concepts and mind-sets of private law do not always capture the essence of committed living arrangements. The application of private law concepts seems to be based on assumptions that are not present in many couple relationships. The thinking in private law is primarily developed with a view to market relationships. In the market, transactions occur in which one service is contractually conditioned upon a counter-service. In family relationships, transfers of assets, goods and services do not normally occur directly between the parties. Instead they are rendered to the family unit as a whole. The parties' services and work efforts are linked together in marriage and cohabitation, as well, but the connection is not of a contractual nature; it is rather grounded in actual economic mechanisms. When one spouse or cohabitant undertakes more than her or his share of the unprofitable consumption tasks in the family she or he could have contributed indirectly to the other party's accumulation of capital. However, such indirect contributions can easily become neglected in legal reasoning. The obligations are of a factual nature, and factual obligations have no name in law; they are not a part of the legal vocabulary.