Niall is a changeling. He's a little fae baby, he just doesn't know it.
Anyway, his mother switched him out for a human baby and she raised that human baby as her own in his place.
Don't question the ways of fairies.
So here's the deets. This character is the true Gallagher babe. They would be the same age as Niall, so 28 years old. They look a lot more like the rest of the family, so preferably with blue eyes and straight dark hair. (Here's visuals of the family: http://hitpoints.org/we-are-bulletproof/in...pic,1183.0.html ) If those faces aren't taken, you're free to use one of those.
Originally, I thought the character would also be male but it could be interesting if the true Gallagher was the only DAUGHTER of the G clan. So either way, I'm a-okay with any gender for this character. Just needs to be a blue eyed 28 year old character raised by fairies in the fairy realm but they're just a human with no special abilities.
The plot idea for this is to have this character looking for their real family after a lifetime of being the black sheep/outcast in their world. And this character is PISSED about being robbed of their true life and true family. So they're hunting the faker out with the full intention of removing him and taking their rightful place as the real Gallagher child.
Ideally this character would make an EXCELLENT hunter as well, especially with their inside knowledge of fairies that most others don't have. This character is eager to make an impression upon their family as well. And they probably want to start their career by killing off Niall. Now, where that actually goes depends on how the two characters interact when they do finally meet. Niall naturally would probably IDENTIFY with this character, because they probably lived the same outsider life, feeling wrong their entire lives. But the similarities could ignite a hatred in the character, or a resistance to see Niall as the same as them. Maybe they start out super antagonistic but grudgingly forge a sibling-like relationship with Niall over time.
ANYWAY that is the idea, feel free to add to it if you have ideas! Toss em at me!