When Cousins Marry

by Joelle Steele

One of the problems with living in the small communities of centuries gone by was that intermarriage between first cousins or marriages involving an uncle/niece or aunt/nephew were not uncommon. Today, we know about recessive genes and some of the hereditary or genetic disorders that can occur if two people possess the same recessive genes and so, for the most part, marriage between such close relatives is pretty much a thing of the past.

However, while the incidence of genetic diseases is higher in children of interfamilial marriages, most of these unions more commonly result in a higher rate of miscarriage; children who are stillborn; children who are less vigorous and therefore less likely to survive infancy or early childhood diseases; children who suffer from ill health throughout their lives; or children who are born with deformities of some kind.

The most common problems with children of married cousins in the old days were miscarriage, still birth, neonatal death, high childhood mortality, and sterility. The most common hereditary or genetic disorders in children born to cousins and other relatives include muscular dystrophy (a group of forty muscular and neuromuscular diseases that cause weakness and atrophy of the muscles), aniridia (a rare defect causing incomplete formation of the iris and therefore loss of vision), multiple polyposis of the colon (numerous malignant polyps in the colon in adults), and neurofibromatosis or Von Recklinghausen disease (a disorder of the nervous system that affects the development and growth of nerve cell tissues and results in tumors that grow on nerves and abnormalities of the skin and bones).

All this said, the actual odds of such problems occurring in a cousin-cousin marriage of any degree are about the same as in marriages in which the two spouses are completely unrelated.