This next one is not an original idea of mine, but it doesn't fit into any fandom, so I'm leaving it right here in the meantime. This idea was crafted by the lovely member Promise, with a few tweaks of my own. The core idea is all them, though.
"Twin Magic" takes place in a fantasy world were there are witches and dragons. Dragons can work any way we want them to, but witches are a little different in this world. With every set of twins is one Witch and one Catalyst. The Witch has inherent magical abilities which she can hone with training. The Catalyst is able to strengthen the spells of other witches just with his or her presence. And when a witch feeds off their own twin's power, they are able to do fantastic things together.
A witch can do magic on her own, of course. And catalyst's blood can be used for potions and alchemical spells. In fact, there were stories of the old days, when catalysts would be hunted down for and killed for their blood, about how the other sibling's magic went mad and dangerous when they former died. This was, of course, before magic of all types was made illegal. It just so happens that, at this time, in this land, there is much fear and suspicion regarding those who can perform magic. If a woman is known to have given birth to twins, often the mother and both babies are burned at the stake, if the parents don't flee the country first.
This is the environment your character grew up in. Your character will be a twin- a witch, as it so happens. But when you were born, in order to protect you, your parents separated you- one taking you, and one taking your brother/sister. As you grew up, you realized at an early age you could do things other children couldn't, but your parents impressed upon you the need not to reveal your powers, so you stifled them.
Years later, in your adult life, suddenly the magic come out. It starts acting crazy and doing things you don't want it to do. And before you know it, you are discovered as a witch, and on the run for your life. In your flight, you come across a dragon. You are amazed you can understand him. He claims to recognize you, and he pleads for your help- but you've never seen a dragon in your life! What on earth is going on?
Alright, I've bet you've already guessed some of the plot. I'm the dragon cause I'm awezum.
1. Make your character and their twin whatever gender you want.
2. There are two ways we can go about this. I can reveal the plot to you, giving you more control over plot twists and so on later, or I can sort of reveal plot elements as they come along. Not saying there will be like, these mind blowing twists, but sometimes it can be fun not to know everything strait out.
3. I'm putting an advanced tag here, so please use proper punctuation, spelling and so forth- you know, stuff that shouldn't even need to be said.
I look forward to chatting with you all!