Customarily wives brought their husbands a substantial dowry, which the husband managed as another family resource. In fact, however, husbands were not free to do as they wished. If nothing else, they faced the powerful obligation to return the dowry and other uxorial property at the end of the marriage (generally by death of a spouse). They could even see a wife claim back her dowry during marriage on the grounds of mismanagement by the husband. The shared economy of the household could fracture, although a wife's claim might also have precluded claims and loss of property to outsiders. The legal problems were evident, and jurists were largely intent on protecting spousal rights.

Brothers often chose to remain together after their father's death, sharing the house and its furnishings, while pursuing common or separate enterprises. Such practices accorded well with advice and aspirations for continued family sharing. However, brothers' contributions were not so easily balanced, and eventually many fraternal households came to a division of assets, for which legal personnel, notaries and lawyers, were essential. Liabilities, which had nominally been shared while together, were also subject to division or denial. Jurists demanded an absolute standard (no separate accounting of holdings, earnings, and expenses) in order to hold liabilities in common. Here the legal presumptions of individual ownership proved deep-seated.

A case from the early fifteenth century shows various themes and legal devices in previous chapters coinciding in one illustrative case: division between brothers, return of dowry, inventory. A sharing economy was giving way to competing claims despite a testament that seemed intent on extending the household that would place a widow with her brother-in-law.

The heir inherited not only the property but also the persona of the deceased, which meant the heir also assumed all debts and liabilities incumbent on the estate. That inherited liability could make an estate burdensome. In the course of the Middle Ages learned law developed the institution of repudiation of inheritance, by which one could decline an impoverished estate. But refusal to inherit ran against expectations of all parties, and could open the door to fraud and deception. Another device, aimed at limiting inherited liabilities so that heirs would accept an estate, was the formal inventory. One's liability would be limited to the contents entered therein and a guaranteed portion would go to the heir. Again, there was reason to fear fraud, and many cities such as Florence limited use of inventories to heirs who were minors. Inventories have proven to be useful historical sources for a variety of purposes, but they have to be used with care. The consilia of jurists on matters involving inventory illustrate what some of the problems were in trusting inventories, which relied for factual evidence on what witnesses, not always disinterested by any means, could provide.

Humanists and moralists, such as Leon Battista Alberti, treated patrimony as a seamless whole, shared by all those in a household, but above all passed from father to son. Their vision is what Bartolus gave legal shape to. It is also substantiated in the fiscal statements heads of household submitted to the government of Florence to determine civic finances. But in fact in law there were subordinate and overlapping rights; sons could have property of their own, designated peculium in law, from several possible sources, including their own labors in the market economy outside the home. Presumed sharing of assets and liabilities by creditors sometimes vanished into devices that separated ownership, leading to real concerns with fraud. Family account books reveal careful maneuvering and accounting by fathers and sons. Sorting out what belonged to a son or whether a father was liable presented legal difficulties as well.

Bartolus of Sassoferrato, the leading jurist of his day, whose influence spanned several centuries, first formulated an equation of family and its property (substantia) that cast an image of family enduring over time in the immediate passage of property from father to son. That tie was so pivotal that a son could be termed, however incorrectly in strict legal terms, as a co-owner of the estate with his father. Disinheritance was difficult to conceive of in these terms, although it was an allowed legal institution. Subsequent jurists followed Bartolus's lead, even though they were likely to face only situations where the paradigmatic passage of haereditas from father to son was not possible.

In late medieval and Renaissance Italian societies, family was conceived as a quasi-corporate entity, continuing across generations. But in law ownership was conceived as an attribute of individuals, and generally of only one person in a household, the paterfamilias. Legal experts worked to accommodate legal notions to the realities of family life, which were close to what anthropologists have come to term an economy of sharing (with multiple and overlapping rights). Law thus came to provide instruments that helped perpetuate families or terminate them. It fell to the paterfamilias to manage property and use legal instruments to do so in order that the patrimony, substantia, could be transmitted to the next generation.

The sharing economy and the legal devices clustered about it became increasingly distinct from ownership vested in one person, which would be at the heart of the sense of property developed in modern law, beginning in the Enlightenment. Overlapping rights were too confusing and liable to keep property from transactions in the increasingly important market economy. The continuity between father and son that Bartolus saw at the heart of the family became harder for others to envision.

One of the central devices for attempting to keep property together and provide for family continuity was the fideicommissum, which was a trust adapted from elements of Roman law. Fideicommissum combined substitution of heirs in agnation, so male lines did not die out, with prohibition of alienation of key family properties extra familiam (making them effectively inalienable). Legal experts had difficulties allowing the Roman fideicommissum, limited to four generations, to endure indefinitely, so they demanded some precise language in testaments of other instruments that established fideicommissa, including clear statement of a testator's intent that property not leave the family, which was at least seen as a laudable goal of legal property management.

Mismanagement of property was always a threat to family survival and patrimonial continuity. Law provided a process by which an imprudent manager could be deemed unfit, even insane (furiosus), and placed under guardianship. While prudence was a quality too slippery to define, it was also generally expected, such that the "prudent man" was a standard of behavior. Here too, things were not simple and conflicts arose, as the sharing economy of the household was under strain by the demands or actions of someone others thought insane.