DCxDP Fenton/Nightingale/Constantines
So, there's some DP fanon about the Fenton/Nightingale bloodline being blessed/cursed by their historical ties to the supernatural (whether that's as witches or witch hunters).
In DC, the Laughing Magician is a bloodline title, and Constantines have either amazing luck or terrible luck. Also, a history of magic users.
What if the Fenton/Nightingales are an offshoot of the Constantines? They started in England as a magically gifted bloodline, which evolved into the Nightingale witches and the Fenton hunters when they reached America.
Equally blessed and cursed, all three bloodlines are susceptible and receptive to otherworldly influence.
Jack Fenton can see ghosts no one else can, which leads him to his career as a ghost hunter and creator of anti-ghost weaponry. He saw something that scared him, something he couldn't touch but could still hurt him, and he invested his life in making himself safe from his personal tormentors.
John Constantine can reach for magic easily, naturally, reflexively. He can instinctually understand summoning circles, he understands demon psychology and learns to manipulate it to his own ends, he summons flames to light his cigarettes because it's easier than finding a lighter. John saw the same monsters Jack did, but he learnt not to fight them, but to manipulate and use them.
The Fenton children carry these traits too. Jazz struggles with normal weaponry, but if someone trained her in magic, she'd be a natural. She has the potential to be a second John Constantine, naturally understanding the psychology of otherworldly entities. If she had more training and less strict morals, she could easily manipulate her way into some very favourable contracts.
Danny, on the other hand, has inherited adaptability and raw power. He doesn't need to analyse his opponent, he can see them in action and steal their moves and return the fire a hundredfold. Danny has learned some skill and refinement, but his ability to adapt is his real strength. He can weaponise anything like his dad, and he can strike precisely like his mum. Also, his luck fluctuates like a Constantine's.
Jazz is a hidden blade and silver tongue, Danny is a nuke.
In a fic, this all could become obvious when John takes in the Fenton children after a Bad Ending. He relates to them too much, but chalks it up to projection. After he introduces them to the JL, Batman somehow gets blood samples. He tells John that they're related, and John realises the Constantine blood is what lead these children to the supernatural, and likely what drove their parents to their profession.
