Reincarnation, sort of...

For an individual to exist, there has been ancestral engagement of 2^n people from his/her precedent n generations. Assuming an average of about 30 years for reproduction at each generation, n would be equal to 33 for the prior 1000 years: the survival of any concurrent individual is a result of commitments of his/her prior 2^33 = 8589934592 individuals, which is a human stockpile huge enough to exhibit almost all types of people.

While recognizing that any individual without exception has an unbroken bloodline inherited from his/her ancestors, let us suppose that there truly is an unbroken bloodline designated as the representative of divine being. Then there likewise is an unbroken bloodline, often referred to as a clan responsible for serving divinities (an example of such would be those whose family emblem is represented by prunus mume), that grants such sacred power to them. There are some more families that have served, generations after generations, their respective local divinities.

Families like these and some secular clans have limited their reproduction to the members among themselves with every 4 to 5 generations apart, resulting in kind of reincarnation of blood.