Is it against public order and good customs for uncle to marry his niece?

According to relevant information, the inquiry shows that the marriage of uncles and nephews violates public order and good customs.

1, consanguineous marriage is an illegal act that violates public order and good customs. Direct blood relatives also include collateral blood relatives within three generations, such as cousins, uncles and nieces, uncles and nieces, etc.

2. uncles and nieces belong to collateral blood relatives within three generations and cannot get married.