"In the US we allow first cousins to marry in 26 states"

I'm speechless...

It is illegal because of religious based morality and society's general disapproval of it, or the thought that it is a form of adultery. In most countries where the main religion allows it, it is not illegal. Some of the blame also falls on the Mormons for pairing together young girls and old men, for adding to the negative stigma that polygamy (or more specifically polygyny - 1 man, multiple wives) receives.

Judging by the map that was linked above, you could go and get married in a country that allows it and then move to Northern Ireland or anywhere else in the UK where your marriage would be recognized.

In the US we allow first cousins to marry in 26 states, gay marriage in less than half that number, and 0 states allow polygamous marriage. I personally think marrying a relative should be considered more taboo, but I guess society would disagree.

But it makes me feel much better to blame the government.