Cousin marriage in the context of "Faustina the Younger"

Christian terminology and theological views of marriage vary by time period, by country, and by the different Christian denominations.

Catholic and Eastern Orthodox Christians consider marriage as a holy sacrament or sacred mystery, while Protestants consider marriage to be a sacred institution or "holy ordinance" of God. However, there have been differing attitudes among denominations and individual Christians towards not only the concept of Christian marriage, but also concerning divorce, remarriage, gender roles, family authority (the "headship" of the husband), the legal status of married women, birth control, marriageable age, cousin marriage, marriage of in-laws, interfaith marriage, same-sex marriage, and polygamy, among other topics, so that in the 21st century there cannot be said to be a single, uniform, worldwide view of marriage among all who profess to be Christians.

Marriage, also called matrimony or wedlock, is a culturally and often legally recognised union between people called spouses. It establishes rights and obligations between them, as well as between them and their children (if any), and between them and their in-laws. It is nearly a cultural universal, but the definition of marriage varies between cultures and religions, and over time. Typically, it is an institution in which interpersonal relationships, usually sexual, are acknowledged or sanctioned. In some cultures, marriage is recommended or considered to be compulsory before pursuing sexual activity. A marriage ceremony is called a wedding, while a private marriage is sometimes called an elopement.

Around the world, there has been a general trend towards ensuring equal rights for women and ending discrimination and harassment against couples who are interethnic, interracial, interfaith, interdenominational, interclass, intercommunity, transnational, and same-sex as well as immigrant couples, couples with an immigrant spouse, and other minority couples. Debates persist regarding the legal status of married women, leniency towards violence within marriage, customs such as dowry and bride price, marriageable age, and criminalization of premarital and extramarital sex. Individuals may marry for several reasons, including legal, social, libidinal, emotional, financial, spiritual, cultural, economic, political, religious, sexual, and romantic purposes. In some areas of the world, arranged marriage, forced marriage, polygyny marriage, polyandry marriage, group marriage, coverture marriage, child marriage, cousin marriage, sibling marriage, teenage marriage, avunculate marriage, incestuous marriage, and bestiality marriage are practiced and legally permissible, while others areas outlaw them to protect human rights. Female age at marriage has proven to be a strong indicator for female autonomy and is continuously used by economic history research.

Consanguinity (from Latin consanguinitas 'blood relationship') is the characteristic of having a kinship with a relative who is descended from a common ancestor.

Many jurisdictions have laws prohibiting people who are closely related by blood from marrying or having sexual relations with each other. The degree of consanguinity that gives rise to this prohibition varies from place to place. On the other hand, around 20% of the global population lives in areas where some consanguinous marriages are preferred. The degree of relationships are also used to determine heirs of an estate according to statutes that govern intestate succession, which also vary from jurisdiction to jurisdiction. In some communities and time periods, cousin marriage is allowed or even encouraged; in others, it is taboo, and considered to be incest.

William III and II (William Henry; Dutch: Willem Hendrik; 4 November 1650 – 8 March 1702), also known as William of Orange, was the sovereign Prince of Orange from birth, Stadtholder of Holland, Zeeland, Utrecht, Guelders, and Overijssel in the Dutch Republic from 1672, and King of England, Ireland, and Scotland from 1689 until his death in 1702. He ruled England, Scotland, and Ireland with his wife, Queen Mary II, and their joint reign is known as that of William and Mary.

William was the only child of William II, Prince of Orange, and Mary, Princess Royal, the daughter of King Charles I of England, Scotland, and Ireland. His father died before his birth, making William III the prince of Orange from birth. In 1677, he married his first cousin Mary, the elder daughter of his maternal uncle James, Duke of York (later King James II).

An avunculate marriage (or uncle/aunt-niece/nephew marriage) is a marriage with a parent's sibling or with one's sibling's child—i.e., an uncle or aunt marrying their niece or nephew. Such a marriage may occur between biological (consanguine) relatives or between persons related by marriage (affinity). In some countries, avunculate marriages are prohibited by law, while in others marriages between such biological relatives are both legal and common, though now far less common.

If the partners in an avunculate marriage are biologically related, they normally have the same genetic relationship as half-siblings, or a grandparent and grandchild—that is they share approximately 25% of their genetic material. (They are therefore more closely related than partners in a marriage between first cousins or between granduncle/grandaunt and grandniece/grandnephew, in which on average the members share 12.5% of inherited genetic material, but less than that of a marriage between, for instance, cousin-siblings, in which the partners share 37.5% of their inherited genetic material.)