Traditional marriage, is quite an interesting concept. Let's look at some longstanding traditional marriage practices:
- Marrying one's cousin (Queen Elizabeth II & Prince Philip; Isaac & Rebekah (of Genesis fame, the Bible book not the band; Jacob & Rachel & Leah of the aforementioned Genesis fame)
- Taking multiple wives (early LDS followers, current FDLS followers, Muslims [optional], various tribes around the world).
- Taking consorts/concubines: (just about every powerful ruler in recorded history, some more obvious than others; a nice recent example is the newly deposed King of Nepal's grandfather's mistress, who has been kindly allowed to continue living in the Royal palace in spite of Nepal becoming a republic).
- Marriage sans clergy: For a long time in Christian Europe, marriages were essentially contracted when a man and a woman either said "I marry you" with or without clergy or witnesses or "I will marry you" which made for a betrothal which didn't turn into a marriage until consummation.
- Marriage based on caste/color/ethnicity/race: You don't marry someone outside the "group"
- The requirement of a dowry-very traditional!
- And the Bible, the OT especially, is full of wonderful examples of traditional marriage. From a man being made to marry his rape victim, to how to treat ones' wives and consorts, the Bible is the definitive source of "traditional" marriage.