Definition
Incestuous bastardy refers to the legal status of a child born of sexual intercourse between two persons whose relationship falls within the degrees of kinship prohibited by law from marrying or cohabiting. The child is illegitimate not merely because the parents were unmarried, but because the union itself was criminally or civilly prohibited on grounds of consanguinity or affinity. Such a child bore a compound disability at common law: the illegitimacy of birth outside lawful wedlock, aggravated by the incestuous character of the parents' relationship.
Common Confusion
INCESTUOUS BASTARDY vs. BASTARDY (GENERAL): All incestuous bastards are bastards, but not all bastards are incestuous. A child born to two unmarried strangers is a bastard at common law; a child born of a brother and sister, or of a parent and child, is an incestuous bastard. The distinction historically carried legal consequences beyond mere illegitimacy — incestuous bastards faced sharper disabilities regarding inheritance and legitimation, and in some jurisdictions could not be legitimated at all, even by the subsequent marriage of the parents, because that marriage itself would have been void.
INCESTUOUS BASTARDY vs. ADULTERINE BASTARDY: These two aggravated forms of illegitimacy are distinct. Adulterine bastardy arises when one or both parents are married to someone else at the time of the child's birth. Incestuous bastardy arises from a prohibited degree of relationship between the parents, regardless of their marital status to third parties. The two categories can overlap — a child born of an incestuous adulterous relationship may be both — but the legal basis for the aggravated status differs.
Recognized Forms
/SUBTYPES
Incestuous bastardy was sometimes further distinguished depending on the nature of the prohibited relationship:
Consanguineous incestuous bastardy: Child born of relations by blood — parent and child, siblings, grandparent and grandchild.
Affinal incestuous bastardy: Child born of relations by marriage or affinity within prohibited degrees — stepparent and stepchild, for example — where the prohibition arose from the legal relationship rather than blood alone. The affinal category was more contested across jurisdictions, and the prohibited degrees varied considerably.
Why It Matters in Research
The term is largely obsolete in modern legal usage. Researchers encountering it should expect to find it concentrated in pre-twentieth-century sources: civil law treatises, ecclesiastical law discussions, Louisiana civil code commentaries, and common law authorities on inheritance and descent.
Several research traps exist. First, the prohibited degrees defining incest varied significantly across jurisdictions and time periods, meaning whether a given child qualified as an incestuous bastard depended entirely on local law. English ecclesiastical courts applied canonical degrees; American states enacted their own statutory tables. A child whose parents' union was incestuous in one state might not have been so classified in another.
Second, the consequences of incestuous bastardy were historically more severe than those of ordinary bastardy. At common law, legitimation by subsequent marriage was available to ordinary bastards in equity and in many civil law jurisdictions. Incestuous bastards could not be legitimated by subsequent marriage because the marriage itself was void ab initio — the union was legally incapable of producing a legitimate status, regardless of what the parties later did. Researchers tracing inheritance disputes or heirship claims in historical probate records should watch for this distinction carefully.
Third, Louisiana occupies a special position in this research area. The Louisiana Civil Code, rooted in French civil law, explicitly defined and categorized incestuous bastards as a recognized legal class, and the term appears in Louisiana jurisprudence in ways that would be unusual in common law states. Black's Law Dictionary's sole surviving definition for this term quotes the Louisiana Civil Code directly, signaling that the term's clearest doctrinal home in American law was the civilian tradition, not the common law.
Fourth, reform of illegitimacy law throughout the twentieth century — driven in part by equal protection doctrine — has substantially eroded the legal significance of all subcategories of bastardy. Modern family codes in most U.S. jurisdictions do not use the term at all.
Historical Dictionary Support
Black's Law Dictionary defines incestuous bastards as "those who are produced by the illegal connection of two persons who are relations within the degrees prohibited by law," citing Louisiana Civil Code article 183. This is the entry's entire doctrinal payload, and it is notably spare.
What Black's does not discuss is the common law treatment of legitimation. English and American common law authorities — including Blackstone's Commentaries and Kent's Commentaries — addressed the incapacity of incestuous bastards to be legitimated, a point the Louisiana code framing does not foreground. The civil law tradition (French, Spanish, and Louisiana) categorized incestuous bastards explicitly as a named class ineligible for legitimation alongside adulterine bastards, a taxonomy that the common law reached by reasoning rather than explicit classification.
Historical dictionaries and treatises agree on the core meaning: the status arises from a prohibited-degree union, not merely from unmarried parentage. They diverge on the consequences and on which degrees of relationship trigger the status. Researchers relying solely on Black's will find the definition but will miss the legitimation disability, the jurisdictional variation in prohibited degrees, and the reform history — all essential to understanding how the term functioned in practice.
Jurisdictional Note
Louisiana provides the most explicit statutory treatment of this term in the American tradition, reflecting its civil law origins. Common law states reached functionally similar results through void marriage doctrine and illegitimacy law without always using the term explicitly. The prohibited degrees of kinship triggering the classification varied by state statute, making direct cross-jurisdictional comparison unreliable without consulting the specific jurisdiction's incest statutes and legitimacy rules for the relevant period.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia: Bastardy; Illegitimacy; Incest; Legitimation