4(Crossover)

An Au where Chloe, Felix and Adrien are siblings and share the same parents but to protect them they had three couples believe they were their children and raise them.

They are children of a shadowhunter couple but both Chloe and Felix are actual children of a demon as the couple made a deal with a demon to be able to have children and the demon requested to have two of their children be his children which they accepted as they really wished for kids.

Anyway the Circle thing started so the couple asked a warlock(Magnus, Ragnor or another) to help them hide their children as they knew two would be killed and they didn't want the third one to be brought into Valentine's mess.

The three ended up being raised by the ones they now believe are their parents until a strange group of people(you can guess who is part of that group as it is basically the same as canon) come to Paris looking for the three of them as they need their help(or some other reason, the writer can decide this).

How things go from here is up to the writer as it is if the miraculous may be connected to the angels or a very old warlock had created them for some reason and they ended up being stolen and later used to fight crime(which were started by one miraculous holder...this made me question how the other previous miraculous holders came to exist as Marinette and Adrien plus the others came to be to fight another miraculous holder...), if there will be any ship, who are Chloe/Adrien/Felix's true parents and if they have any connection to any of Shadowhunters main characters, etc.