It depends upon where you live and the laws that the area has. For example, the state of Massachusetts (US) is fine with not only same sex marriages but those of cousins.
If you mean from a genetic standpoint, the risk of a genetic disease or malformation in their off-spring is greater than those that are non-related and less than those that are siblings, from what I have read. To be honest, I’m not sure if that is true. Anyone can bear a child and have no clue what type of ancestral genetics may be thrown into the mixture unless an extensive study is done on the front end.
My guess is that the stigma of marrying a cousin is a social taboo created at some point in history and lives on today without any re-evaluation.
I come from a family where 2nd and 3rd cousins marrying was common for a few generations, even a few 1st cousins squeaked in there. To my knowledge, no one had/has any rare medical conditions or noticeable mutations.
If I remember correctly genetic problems occur about 4 to 5% of the time in offspring from cousins. The normal population is around 2%.
Is it ok? Well, a lot of people consider it taboo. I have a friend whose parents are first cousins and some parts of the US it happened more than others. Among royalty in various countries close relations often married to keep the blood lines “pure.”
The U.S. is virtually alone among developed nations in outlawing marriage among first cousins.…A recent review (Bennett et al, Journal of Genetic Counseling, 2002) says that, on average, offspring of first-cousin unions have a 2 to 3 percent greater risk of birth defects than the general population, and a little over 4 percent greater risk of early death.
If you get far back enough in everyone’s family trees, there’s quite a bit of intermarrying going on. Still happens nowadays (my grandparents were second cousins, which obviously explains me ;-) ).
As others have said, depends on the state (although as @gasman‘s quote notes, it’s far more common outside of the U.S.); @lillycoyote‘s link is a good start to figure out where cousin hitching is A-ok.
It is absolutely OK to marry your cousin and is legal in many countries. Historically, and still in some situations, it is/was used to keep property in the family. Families used to be a larger, especially in rural areas. Genetic problems are actually rather rare with offspring of cousins. It is more the ‘icky’ factor that people have trouble with.
“The absolute risk to first cousins having a child with a recessive genetic condition is about three in every 100 births, unless they have a family history of an autosomal recessive disorder, in which case the risk may be higher. When we also include the background risk of having a child with any type of congenital or genetic disorder, which applies in every pregnancy, the overall risk to first cousins rises to about six in every 100 births, i.e. double the risk in the general population. The great majority of pregnancies do not result in abnormalities.”
Depends on where you live. In the UK it’s legal to marry your cousin, and for same-sex couples it’s legal to have a civil partnership with your cousin.
To be honest, these laws about not marrying relatives make no sense when it’s a same-sex couple. They’re designed to prevent the increased risk of birth defects but obviously that’s not relevant to a same-sex couple. The only reason I can think of to prevent it, aside from people thinking it’s just “icky”, is that the right to marry relatives can’t be given to one group and not another without accusations of inequality.
From a sociological perspective, the only negative I can think of is that it prevents bonds being made between families. And since children are becoming increasingly disassociated from marriage, the matter of offspring is becoming less important.
@cazzie No, I did not read your link, but I saw what you wrote and it agreed with what I had written in my first answer. I think @gasman‘s wording in his answer and from his link, which I did skim, leads people to believe it is only a 2% increase, which is much different than a 100% increase. But, since the numbers are rather small anyway, it is minimal either way. Anyway, that is why I addressed @gasman.
I don’t care who marries who providing it is consual and if there is a high risk your kids will be mutated (I don’t know if there is or if it’s just a myth where cousins are concerned) then you seriously think about adoption!
In some ways, it isn’t entirely rational to forbid cousin marriage, if the purpose of the prohibition is that their offspring have an increased risk of some kind of genetic disorder.
Ashkenazi Jews and, I just learned, French-Canadians and the Cajun community of Louisiana have the same carrier rate for the gene for Tay-Sachs, one in 27. And also, apparently, new research has shown that Irish Americans have a carrier rate for the Tay-Sachs gene of 1 in 50. The carrier rate for Tay-sachs in the general population, excluding these particular groups is 1 in 250. If two carriers reproduce, they have a 1 in 4 chance of producing a child with Tay-Sachs and, whether one or both parents is a carrier, the risk for producing a child who is a carrier is a 2 in 4, producing another genetic time bomb, yet it is not against the law for Ashkenazis, or Jews who may have Ashkenazi ancestry, or French-Canadians, or Cajuns or Irish Americans to marry, and of course, it certainly shouldn’t be, even though their chances of having a child with a genetic defect, either a carrier or at worst a child with Tay-Sachs, is greater than the risk of producing offspring with genetic defects is among first cousins who marry.