Can relatives of one family marry relatives of another family?
Question:
Is it morally legal for a father, brother, and son to be interested in marriage with three unrelated females that just so happen to be a mother, sister, and daughter, related to each other, but not to the men? If not, which ones and why not?
Answer:
Though we are not under the Old Law, this is the only law that has details similar to your question. In Numbers 18:6, a person was forbidden to have sexual relations with a close blood relative. This was spelled out in detail in Numbers 18:7-18. Since the women in your scenario are unrelated to the men, this law does not apply.
Nor do I know of a civil law that would forbid such unions.