Basic Trope: In order to ensure a "pure" royal lineage, members of royal and noble families have Arranged Marriages with members of their own family.
- Straight: Prince Bob, the crown prince of Tropestan marries his aunt, Princess Alice of Wikistan.
- Exaggerated: Prince Bob marries his twin sister, Princess Alice
- Downplayed:
- Prince Bob marries Princess Alice, who is his cousin once removed.
- Alice and Bob are half siblings and illegitimate children of the king. They are not royalty but still a cut above the average commoner. There shared heritage is the reason the two fall in love on the first place.
- Justified:
- The Royal Family of Tropestan wants to ensure a pure royal lineage, so titles and property stay within the family, and so that there is no dispute as to who's next in line for the crown.
- Everyone Is Related anyway in this universe, so looking outside the family for a spouse is moot.
- Inverted: Prince Bob marries Alice, a commoner, who is not even tangentially related to the royal family.
- Subverted: Princess Alice marries her brother, Prince Bob, but it's later revealed that she was adopted.
- Double Subverted: She was adopted because she was illegitimate. She's Bob's half sister.
- Parodied: The royal family tree doesn't fork at all; it's just a straight column.
- Zig Zagged: ???
- Averted:
- The Royal Family of Tropestan doesn't arrange marriages between relatives.
- Tropestan is not a monarchy.
- Tropestan is an Elective Monarchy, the nobility members are heavily pushed towards marrying commoners and checking ancestry of their potential spouses to the furthest available extent, and the children of the current king/queen are legally prevented from becoming rulers immediately afterwards.
- Enforced: It's Historical Fiction based on a time when this really happened.
- Lampshaded: "Our parents are cousins, our grandparents and great-grandparents were cousins... we'll have to continue the lineage and the tradition, shan't we?"
- Invoked: ???
- Exploited: ???
- Defied: The laws of Tropestan specifically forbid close relatives to marry, and that includes the royal family.
- Discussed: "Maybe our future monarchs wouldn't be so kooky and fragile-bodied if the crown prince, for once, married a commoner or a foreigner?"
- Conversed: "Those fantasy dynasties hook up with their relatives all the time. Huh, no wonder they don't tend to produce good rulers all the time..."
- Implied: Alice's and Bob's fathers look a lot alike and are very close, although it's never stated whether or not they're brothers, and by extension if their married children are cousins.
- Deconstructed: Generations of inbreeding cause many debilitating genetic disorders to crop up in the royal family tree.
- Reconstructed: But it also reinforces the positive genetic traits the royal family is aiming for. Alice and Bob's child may have flipper hands and brittle bones, but when he opens his mouth to speak everyone is astonished by his intellect and eloquence.
Oh, no, dear troper, that's not an unfocused gaze! Our beloved king is simply contemplating the future! He constantly shakes all over with vitality and passion! Those extra fingers are symbolic of how firmly he grasps the fate of the people! Drool? Nay, 'tis nobility leaking out of him. All over him. Clearly, you need go back to Royal Inbreeding and learn a few things!
