1

one has been cursed.

2

one has been kidnapped by a dragon.

3

their family does not approve of the other.

4

one is actually a ghost.

5

one has caught the plague.

6

of religious custom.

7

of societal norms.

8

one is actually a vampire.

9

one is actually a werewolf.

10

one is being held captive by a hag.