[quote="mothom, post:1, topic:226191"]
I have a relative, he's a Pentecostal preacher, who's married to his step daughter. She was ~3 years old when he married her mother. He and her mother have 3 daughters. Before his step daughter became an adult, he and her mother divorced. The step daughter was finished being raised by her grand parents. Later on they married and now have 2 boys. I was wondering if this is a legitimate marriage, biblically speaking, or if they're living in fornication like the man in the 5th chapt. of 1st Corinthians who took his father's wife? I'm inclined to think this is all wrong.
The term for this is *affinity *in the direct line. Affinity is a relationship "arising from the carnal intercourse of a man and a woman, sufficient for the generation of children, whereby the man becomes related to the woman's blood-relatives and the woman to the man's."
The Catholic Church does NOT allow marriage in the direct line (parent, child, grandparent, etc) from a relationship arising from affinity.
The Church used to prohibit marriage in the collateral line as well (siblings, aunts/uncles, etc) but no longer prohibits marriage in the collateral line based on affinity.
Can. 1092 Affinity in the direct line in any degree invalidates a marriage.
Here is an article on biblical affinity: