In the game we're playing right now, my daughter made a vampire family and werewolf family, and placed them both in apartments in the same building, with the idea of a "forbidden love" story. The vampire family has a young female and werewolf family has a young male, and her goal was to have them fall in love and get married, while their family hates each other.
It's a pretty fun game to play, but certainly a challenge. The young lovers really hated each other at first. Whenever one of them said something nice to the other , it only made them hate each other more! So we did get them to eventually become friends and lovers, but it was a LOT of work !
It would have made better sense for roleplay if they eloped, but we decided to have a wedding, so we could get utter chaos from the rival families. The vampire bride's parents didn't even show up to the wedding. The groom's parents did, but his sisters did not come. Oh, and the vampire bride's grandpa did come, but he stayed too long and died from sunlight exposure in the morning. (So my daughter engraved his urn to say "Our marriage really did kill him.")
The werewolf's grandma died too. Her tombstome disappeared, but I was able to find her ghost through a cheat. The couple invited her ghost to live with them, and then invited the vampire grandpa ghost to live with them. So now the forbidden lovers have rival grandparents living with them (and their apartment is in the same building as the vampire and werewolf families, so lots of nasty sentiments go on in the hallway, and in their apartment.)
They have two children so far. (First a boy, and later a girl.) Both babies turned out as werewolves, but we keep saying that the vampire mom is in denial and insists they're really vampire babies. Vampire mom actually had a negative reaction to both babies, but turned green soon (after she convinced herself they were really babies).
Things got a little out of control during the last full moon. Between the werewolves and the ghosts, vampire bride was in a near constant state of terror, and developed a huge grudge against her werewolf husband. Then we had to go back to work fixing that relationship! We can't let them get divorced yet. They don't have a vampire baby yet! And besides, this family is so fun to play. We're always making crazy jokes about what they're really thinking.