Judaism, some branches of Christianity, Islam, Dravidian Hinduism, Buddhism, Zoroastrianism, and the Confucian tradition allow consanguineous marriages.
The Bible does not prohibit first-cousin marriages. But the age-old laws of the Roman Catholic and Eastern Orthodox churches reject such marriages.
During the Reformation, the Church of England followed Protestantism's "sola scripture" (Scripture alone) principle and returned to biblical law, which also binds traditional Jews.
Buddhism originated in North India in the third century B.C., and the Prince Buddha is reputed to have married his first cousin. Perhaps, for this reason, there is no overall rejection of consanguineous marriage within the Buddhist tradition.
It was rare for a Parsi to marry out of the family; marriage between cousins (a marriage made in heaven) was both practical and expected, while incestuous marriage was illegal.
The position of first cousins under the Special Marriage Act 1954 is in accord with the Hindu Marriage Act 1955, which does not allow marriage with any first cousin.
But, the Consanguinity of marriages is prevalent in some communities in south India. At the national level, prevalence of cousin marriages are 14%. The overall figure conceals the regional and religious differences.
Marriage between first cousins was generally allowed during China's dynastic era. However, in 1981, China banned all marriages between first cousins. The purpose of the ban was to avoid congenital disabilities that stem from consanguineous marriages.
The Quran, in chapter 4:23, leaves out mention of one's cousins in its list of those relatives with whom one should not marry. There is no explicit permission to marry a cousin.
Forbidden to you (are) your mothers and your daughters and your sisters and your father's sisters and your mother's sisters and daughters (of) brothers, and daughters (of) sisters and (the) mothers who nursed you and your sisters from the nursing and mothers (of) your wives and your step-daughters who (are) in your guardianship of your women whom you had relations with them, but if not you had relations with them, then (there is) no sin on you. And wives (of) your sons, those who (are) from your loins and that you gather together [between] two sisters except what has passed before. Indeed, Allah is Oft-Forgiving, Most-Merciful.
However, the Quran in chapter 33:50, in discussing the exclusive marital rights of the Prophet Muhammad, explicitly permits him to marry his first cousins.
O Prophet! Indeed, We [We] have made lawful to you your wives (to) whom you have given their bridal money and whom you rightfully possess from those (whom) Allah has given to you, and (the) daughters (of) your paternal uncles and (the) daughters (of) your paternal aunts and (the) daughters (of) your maternal uncles and (the) daughters (of) your maternal aunts who emigrated with you, and a woman believing if she gives herself to the Prophet if wishes the Prophet to marry her - only for you, excluding the believers. Indeed, We know what We have made obligatory upon them concerning their wives and whom they rightfully possess, that should not be uncomfortable on you. And Allah is Oft-Forgiving, Most Merciful
Prophet Muhammad married his cousin Zaynab bint Jahsh, the daughter of Umaimah bint Abd al-Muttalib (a sister of the Prophet's father).
The Prophet also allowed the marriage of his daughter, Fatimah, to his first cousin, Ali ibn Abi Talib. The second Caliph, Umar ibn al-Khattab, also married his cousin, Atikah bint Zayd ibn Amr ibn Nufayl.
The main reason to ban first-cousin marriages is said to be medical. But Professor Alan Bittles of Murdoch University and Edith Cowan University in Australia studied cousin marriages for the past 30 years and challenged this. He said 10.4 percent of people worldwide are married to a close relative or are the children of such a marriage. "This equates to over 700 million people," Bittles says.
However, in the United States, Several states prohibit cousin marriage. 24 U.S. states prohibit marriages between first cousins, 19 U.S. states allow marriages between first cousins, and seven U.S. states allow only some marriages between first cousins.
Six states prohibit first-cousin-once-removed marriages. In addition, some states prohibiting cousin marriage recognize marriages performed in other states. Still, laws also exist that explicitly void all foreign cousin marriages or marriages conducted by state residents out of state.
States that allow first-cousin marriages
Alabama, California, Colorado, Connecticut, the District of Columbia, Florida, Georgia, Hawaii, Maryland, Massachusetts, New Jersey, New York, New Mexico, Rhode Island, South Carolina, Tennessee, Virginia, and Vermont.
States where first-cousin marriages are not allowed
Alaska, Arkansas, Delaware, Idaho, Illinois, Iowa, Kansas, Kentucky, Mississippi, Missouri, Louisiana, Michigan, Montana, Nebraska, Nevada, North Hampshire, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, South Dakota, Texas, Washington, West Virginia, and Wyoming.
Conditional First Cousin Marriages
Arizona: Only if both parties are 65 or older or one is infertile.
Indiana: Only if both parties are 65 or older or one is infertile.
Maine: Proof of genetic counseling from a genetic counselor.
Minnesota: Only certain types.
Utah: Only if both parties are 65 or older, or both are 55 or older, with a district court finding of infertility of either party.
Wisconsin: Only if the woman is at least 55 or either is permanently sterile.
Despite their positions on these issues, faith-based communities have followed U.S. laws. However, many have found a way to bypass state laws. For instance, residents living in states that do not allow first-cousin marriages often go to states to register such unions in states that will enable them. But, those performing such marriages should note that in several states, such marriages are not valid.