Definition
Affinity is the legal relationship created by marriage between one spouse and the blood relatives of the other spouse. It is not a blood relationship but a status relationship: it arises solely from the marriage and exists between, for example, a husband and his wife's siblings, parents, and cousins — and symmetrically between the wife and the husband's blood kindred. Affinity does not exist between the spouses themselves, nor between the blood relatives of each spouse toward one another.
The primary legal significance of affinity lies in three areas: (1) prohibited degrees of marriage, where affinity relationships have historically barred remarriage to a deceased or divorced spouse's relatives; (2) juror disqualification, where a juror's affinity to a party may warrant recusal; and (3) intestacy and inheritance statutes, where the term occasionally appears to define or exclude classes of relatives.
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Common Language
Modern common usage (Wiktionary): A natural attraction or feeling of kinship to a person or thing; also, a family relationship through marriage as opposed to consanguinity.
Historical common usage (Webster's 1913): Relationship by marriage, in contradistinction to consanguinity or relationship by blood; also used more broadly to mean close agreement, resemblance, or connection between things generally.
The ordinary English senses of affinity — a felt attraction, a general resemblance, or a loose kinship — are far broader than the legal sense. In law, affinity is a precise relational status with defined consequences; it does not arise from sentiment or informal association. A researcher encountering the word in a legal instrument or court opinion should not read it as merely signifying closeness or similarity.
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Common Confusion
Affinity is frequently confused with consanguinity. Consanguinity denotes relationship by blood — the connection between persons who share a common ancestor. Affinity denotes relationship by marriage — the connection between a spouse and the blood relatives of the other spouse. The two concepts operate in parallel in prohibited-degrees law, but they are legally distinct: consanguinity can never be dissolved, while affinity, in some jurisdictions and for some purposes, terminates upon dissolution of the marriage that created it. Historical sources sometimes treat them together under the heading of "relationship," which can obscure the distinction for modern researchers.
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Recognized Forms
/SUBTYPES
The historical common law recognized three formal gradations of affinity, preserved consistently across the major dictionaries:
Direct affinity: The relationship between a spouse and the blood relatives of the other spouse. This is the primary and most legally operative form — the husband to his wife's siblings, the wife to her husband's parents, and so forth.
Secondary affinity: The relationship between a spouse and the spouses of the other spouse's blood relatives. For example, the relationship of a husband to the wife of his wife's brother. This form was recognized doctrinally but carried limited legal weight in most contexts.
Collateral (or remote) affinity: The relationship between a spouse and the blood relatives of the other spouse's blood relatives — a more attenuated connection. Courts and legislatures rarely extended legal consequences to this degree.
In modern practice, statutory schemes governing prohibited marriages and juror disqualification typically specify affinity by degree rather than by this tripartite classification, and many jurisdictions have abandoned the secondary and collateral categories entirely.
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Why It Matters in Research
Affinity is one of the terms most affected by statutory change over the past century, and its legal consequences vary significantly across time, jurisdiction, and subject matter. Researchers face three specific hazards.
First, the prohibited-degrees problem. At common law and in early American statutes, affinity relationships prohibited a wide range of marriages — a man could not marry his deceased wife's sister, for example. Many jurisdictions have substantially narrowed or entirely abolished affinity-based marriage prohibitions, but historical instruments (wills, family settlements, guardianship orders) may have been drafted against the older, broader framework. A document that refers to "persons within the prohibited degrees of affinity" requires knowledge of which jurisdiction's law applied and at which historical moment.
Second, dissolution and its effect on affinity. Whether affinity survives the death of the spouse who created it — or a divorce — is unsettled across jurisdictions and periods. Some courts held that affinity dissolves when the marriage ends; others held it permanent. This distinction matters acutely in prohibited-marriage cases (can a widower marry his deceased wife's sister?) and in juror-disqualification disputes. Historical sources do not always flag this divergence.
Third, the juror-disqualification context. Affinity appears regularly in older case law on juror qualification. The degree of affinity required to disqualify a juror has varied by statute and by judicial decision. Researchers working in appellate records from the nineteenth and early twentieth centuries will encounter affinity arguments that turn on which gradation — direct, secondary, or collateral — was at issue, and how the relevant statute defined its reach.
The term also appears in intestacy and probate contexts, though generally to exclude affinal relatives rather than to include them. A statutory phrase like "heirs of the blood" was typically read to exclude relatives by affinity entirely.
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Historical Dictionary Support
The five source dictionaries are in strong agreement on the core definition: affinity is the relationship created by marriage between each spouse and the blood kindred of the other, and it is distinguished from consanguinity. All sources that address the taxonomy adopt the same tripartite division into direct, secondary, and collateral affinity, tracing to Blackstone and Coke.
Bouvier's formulation is the most practically useful, emphasizing both the bilateral nature of the relationship (each spouse gains affinity with the other's kin) and its distinction from consanguinity. Burrill's adds scholarly texture by citing Coke on Littleton and Blackstone directly, grounding the concept in common law authority. Black's Second Edition is the most operationally specific, noting the "at common law" qualifier — a signal, important for researchers, that statutory modifications had already altered the doctrine by the time of that edition's publication.
Anderson's entry is notably spare ("Relation by marriage") and offers no independent analytical value. It reflects the dictionary's general tendency toward compression rather than a finding that the term was uncontested.
None of the historical dictionaries address the question of whether affinity survives dissolution of marriage, which is precisely the question that generated the most litigation. This is a gap researchers should flag: the historical sources describe the formation of affinity but are largely silent on its termination.
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Jurisdictional Note
Modern American jurisdictions have largely abandoned or narrowed affinity-based marriage prohibitions, and the tripartite common law classification has little statutory footprint today. English law historically maintained broader affinity restrictions than most American states. In juror-disqualification contexts, statutory definitions of qualifying affinity vary: some states specify degree (e.g., within the third degree), while others reference affinity without degree limitation, leaving courts to apply common law gradations. Researchers should not assume that a single uniform doctrine governs across jurisdictions or periods.
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Encyclopedia Cross-Reference
Marriage — Capacity to Marry (Age, Consanguinity, Affinity), The Law Mind Family Law Encyclopedia
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