The focus of Athenian family history shifted from patrilineal clans to matrimonial families in the 1980's. Behind this change in scenes, a question has been left unanswered: i.e. was the oikos, the family, incorporated into the Athenian legal system as the basic unit of the constitution, and if so, who were the members of this legal oikos? This issue extends back to 1944, when H. J Wolff emphasized the importance of the oikos as a constitutional unit of the polis. Opposing this view, D. MacDowell, in 1981, maintained that the oikos had no place in the Athenian legal framework. He argued that the Athenian law never employed the term oikos to denote family membership and that the Athenian legal system was based on individuals instead of family units. This view has been regarded controversial as it has been seen as containing irresolvable contradictions to the prevailing views on the importance of family units in Athenian law and life. In this paper, I will try to resolve the apparent contradiction in MacDowell's argument by suggesting that the oikos was regarded as a legal unit in the 4th century Athenian polis, and that the oikos in this legal sense was not a matrimonial household that Aristotle defined as the minimum unit of the polis community in the Politics, but a unit that consisted of family members sharing the same bloodline. Pace MacDowell, the oikos including family members indeed appears in the Athenian law on 'the empty house' (eremos oikos). The usage of the term 'oihos' in the law court speeches, especially in the cases concerning the estates of Hagnias (Is.11, Dem. 43), shows that the oikos was an entity that consisted of family members, property, ancestral cults, and hereditary names. The 'empty house' in the Athenian law, therefore, should be regarded not as deserted property, nor as a vacant building, but as an entire unit that had lost its members, property, and/or religious continuity, A man's house was regarded empty after his death if he left neither sons nor daughters. An archon was to protect orphans and epikleroi, but wives were excluded from the archon's protection, and, once her husband's oikos had become 'empty', a wife could not retain her rights as a member of the family unit unless she was pregnant. This means that a wife was not an autonomous part of the marital family, and could not retain her position after the death of her husband. This emphasis on direct lines of descent and the exclusion of wives from their marital families is reflected in the strong ties that married daughters and sisters retained with their natal families. Recent studies attest that widows usually returned to her natal families and remarried from there. The processes of divorce and remarriage also show that the natal families retained rights to the women of their stock. Funeral law also prescribes that women retained their rights and obligations to their family of origin regardless of their marital status. Furthermore, the demotics of women tell us that women were initially identified through their father's names and demotics, which were used even after their marriage and death in predominance to those of their husbands. The incorporation of women into their husband's oikos was imperfect and temporally limited. Oikos membership in the narrow legal sense did not include the wife and consisted of a man and his descendants. The law court speeches, however, are full of episodes telling the importance of the marital household (oikia) and the affection therein in justifying family matters. This discrepancy between the hereditary membership in the oikos and actual family affection developed in a marriage is visualized in family tombstones as well The Athenian popular court can be understood as a place where the ideology of hereditary and legal oikos was negotiated with the intimacy accumulated in the household. The portraits of the families depicted in the law courts were the product of this process of negotiation.