Since around the end of the undocument war humanity obtained powers either through a miracle, or mutation. Each theory different from the last.
These powers were different ranging from person to person. But similar throughout an entire family tree.
For example, Someone could have the ability to manipulate ice or any type of liquid. Then someone else in their family has the ability to manipulate water.
There are also rare abilities that aren't really common around most citizens of the world. These rare abilities mainly reside in Prestigous Families. For example the Winchesters have a rare ability only their family can use and it involves "Aura". Another example would be the Roswell family who can create a magnetic pulse around their body.
P.S. - Do try not to make your powers op in anyway have them limited to full use depending on your characters age, practice(practice in the ability), and physical health.
- If you want a rare ability if you have a family tree that only they can use create one. It must also follow the p.s. note and rules above. Be creative if you would like.
People with powers are common in most if not all city-states. However most are forced to be a part of that city-states self-defense force. Depending the power rating(how powerful it is) and control of such power the higher the rank. They are treated as equal citizens and are free to use their powers so long as it isn't used for violence or terrorism, etc. Or they will be confined in court.