Recently, Muslims in the U.K. were outraged when it was announced that the prevalence of marriages between cousins was responsible for a large number of defective children being born in their community. While it is true that cousin marriages slightly increase chances of children being born with genetic defects, among Muslims, most people are the products of decades of cousin marriages. If a child’s great grandparents, as well as grandparents were first cousins, it significantly increases the chances of that child having more defects than one whose forebears were not first cousins. I know many families in which children are either totally deaf or totally near-sighted, and they were shocked when doctors told them that inbreeding was to blame. For this reason, cousin marriages are banned in 26 states in the U.S., while most Hindu sects do not allow marriages between cousins. This proves that even three thousand years ago, people realized that marriage among near relatives was harmful.
So how do you convince people not to marry their cousins? The mullah will immediately say that it is a Jewish conspiracy against Islam, forgetting that it was the Holy Prophet (saw) himself who said, “Don’t marry a near relative (such as a first cousin) as in that case a child is born weak (i.e. defective)”, as quoted by Imam Ghazali in ‘Ihya Ulum id Din’.
But I doubt if in Pakistan people will marry outside their families, since in most cases, particularly in rural areas, the spouses of children are chosen by their parents when they’re hardly two or three years old.