The major civilizations of Eurasia found different ways to integrate (a) systems of kinship and descent, with roots stretching back into the deep history of Neolithic demic expansions, (b) states and state formation, along meta-ethnic frontiers and elsewhere, and (c) major world religions. In Classical Greece and Rome, devotion to patrilineal descent groups was edged out by wider loyalties to the city state. And in Late Antiquity and later, Christianity in Europe would also encourage the weakening of extended family ties. China took a different path, upholding state patriarchy and the rule of the clan, and eventually suppressing Buddhist monasteries.
In the case of the Islamic world, something about (a) kinship, marriage, and descent is reflected in this map, which shows percentages of consanguineal marriages (first and second cousins) around the world today.
Southern India has a tradition where men from group A take wives from group B and vice versa, which can result after a generation in cousin marriage. (Aboriginal Australia has similar marriage rules.) The Islamic Middle East and Central Asia, a culture area formed in the course of the great Arab conquests of the seventh and eighth centuries, have another kind of cousin marriage, where marriages are kept within a patriline: i.e. it is common for a man to marry his father’s brother’s daughter. Such marriages are not directly encouraged by Muslim law. However Muslim rules of inheritance may indirectly encourage them. Under traditional Muslim law, each daughter gets one share of inheritance; each son gets two shares. This is a better deal for women than the one where sons get everything (as in traditional China, for example). But it means that a lineage can expect to lose a third of its property with each generation if it lets daughters marry out.
There is probably more going on, though, than just inheritance law: marriage within the patrilineage long predates the rise of Islam among Near Eastern pastoralists. It is probably connected with another characteristic of this culture area: an intense culture of honor, including a high premium on female purity (guaranteeing the integrity of the patrilineage). To allow a daughter or sister to be seduced by an outsider is deeply dishonorable. But even a legitimate marriage to an outsider carries some shame, putting the wife-giving family in an inferior relation to the wife-takers. Not letting daughters and sisters marry outside the patriline is one way for a lineage to advertise its honor.
One of the classic studies of the culture of honor in the Mediterranean is entitled The Fate of Shechem. The reference is to the story of Shechem and Dinah and her brothers in Genesis 34. Shechem, prince of the city, seduces (or maybe rapes) Dinah. His father, the king, proposes to make things right: “Make marriages with us; give your daughters to us, and take our daughters for yourselves. You shall dwell with us; and the land shall be open to you; dwell and trade in it, and get property in it.” Dinah’s brothers, who are Jacob’s sons, pretend to agree to the bargain, but use a ruse to kill Shechem and his father and plunder their city. Jacob is upset that he has acquired a whole new set of enemies, but his sons ask “Shall he make our sister a whore?” A remorseless sense of honor, a determination to avoid a humiliating sexual dependency, trumps the need for a marital alliance.