
Quoting
Taxing Matters
It appears that the answer is yes, which is why I mentioned it.
Iran evidently allows marriages for children as young as 9. Yemen and Micronesia have no statute with a minimum age for marriage. And some countries like India, while having a marriage age that is older (18 for women, 21 for men in India), marriages at younger ages are recognized unless the person who was under the marriage age petitions for annullment.
There are also nations that have eliminated laws that bar most or all incest, including but not limited to Portugal, Spain, and Serbia. Thus it is my understanding that an incestual marriage would not be illegal.