Consanguineous marriages are unions between individuals who are related as second cousins or closer, sharing at least one common ancestor. Such marriages involve biological kinship between the partners and are often categorized according to the degree of relatedness, such as uncle–niece, aunt–nephew, or first-cousin marriages. From the perspective of biological diversity in human populations, consanguineous marriages are significant because they increase the probability that both partners carry identical alleles inherited from a common ancestor, thereby increasing homozygosity in the offspring. This has implications for the expression of recessive genetic traits and certain hereditary disorders. In India, consanguineous marriages vary widely across regions, religions, and communities, reflecting deep-rooted cultural traditions. They are more prevalent in South India than in North India. One of the most common forms in southern states such as Tamil Nadu, Karnataka, and Andhra Pradesh is the cross-cousin marriage. Cross-cousin marriage refers to a union between the children of a brother and a sister, such as a man marrying his mother’s brother’s daughter (MBD) or father’s sister’s daughter (FSD). For example, in many Dravidian kinship systems, a man may traditionally marry his maternal uncle’s daughter, and this form of alliance