Kekkei Genkai (Blood Inheritance Limit)
Throughout the infinite villages of Naruto there lay many clans, each of these clans has their own unique traits that make them uniquely, identifiably theirs. However, there are only a few clans who can say that they have a kekkai genkai, or advanced bloodline in their clan. An advanced bloodline refers to something that is passed down generation to generation in a specific clan, it is in the genetic makeup of each clan that can not be duplicated or imitated by any method. Advanced bloodlines are always used to the advantage of the user, improving their chances in combat and making them a very worthy opponent. The rulers and warlords of each country had taken advantage of each bloodline to it's fullest extent to help their chances in war, and thus the people began to associate advanded bloodlines with war and pain. This reached the point of hatred towards anybody who was part of these special clans resulting in the genocide of these individuals and whole families, as was the case with Haku.
now these abilitys are specail and are a very rare trait in a ninja so there can only be a limited number of members with the blood line trait. at the bottom of each blood line there will be a number saying (some number)/(some number) the number to the left is how many of that clan there are currently and the number to the right is how many of that clan there can be
example if there was 4/5 that would mean there are 4 poeple currently in that clan and 5 is the maximum number of poeple that can have that blood line, so for this blood line only one more person could join it until some one in that blood line dies if some one dies in that blood line then a new user may take there place but its first come first serve so be fast.