Incest is the act of engaging in sexual intercourse with one's direct family member (siblings, parents, offspring). It is a great cultural taboo both in the Seven Kingdoms and the lands beyond the Wall. Intermarriage between first cousins is actually not considered "incest" in Westerosi society. A prominent example is that Tywin Lannister married his own first cousin Joanna Lannister, mother of all three of his children. Alongside kinslaying and the violation of guest right, incest is proscribed by every major religion in Westeros. Children born of incest are deemed abominations.