#leviticus forbids marrying anyone within 3 degrees of kinship. Parents, children, grandchildren, grandparents, siblings, half-siblings, step-children/parents, in-laws: all forbidden. First cousins are the closest relations the Bible allows to marry, but "allowed" doesn't mean "good idea".

First cousin marriages are common around the world and were fairly common in the West until the 20th century. In my opinion (and I'm not alone) continuous genetic deterioration + cultural ick-factor makes first-cousin marriage a really bad idea today.

https://soilfromstone.blogspot.....com/2009/12/prohibi