sharing the same blood

Nature implies same; being implies differentiated from one another. Blood/bloma/bhel - "to thrive; bloom" implies the growth effort of each native within nature to thrive among each other...as seen by ones off-spring aka the fruit of ones labor.

Entrance blood banks and transfusions to curtail the thriving of each by mixing many aka "mud-blood". This is also why an alchemist utilizes menstrual blood for pollution during synthesis.