Blood-drop consanguinity first appeared in the Three Kingdoms period. At that time, blood was dripped on the bones of ancestors by dripping bones. If the blood is deep, it means there is blood relationship.
This was recorded by Song Ci, a forensic scientist in the Song Dynasty, in his book Injustice Collection. It is said that Song Ci proposed the method of parent-child litigation for the living.
Is to drop the blood of two people into a bowl of clear water, observe whether the blood is harmonious and judge whether they are related by blood. The reason why the ancients believed in blood-dropping to recognize relatives was because they believed that children and parents were of the same kind of bone blood, so their blood would naturally mate. And no one has ever doubted, even in China's forensic works in the Song Dynasty, this ancient identification method was recorded.
In fact, as long as two different blood types are mixed together, at least half of the red blood cells will agglutinate. Only when two identical blood types meet can they fuse without any agglutination. Therefore, using "blood test" as evidence, blood with blood relationship may not be able to fuse, but blood without blood relationship may also fuse. I really don't know how many unjust cases have been produced and how many real murderers have been spared.
Speaking of which, I remembered an interesting thing. When I was a child, my hand was cut and I happened to kill pigs at home, so I put my blood together to play. I cried all day and asked my family who gave birth to me. Until now, my mother still makes fun of me about it.
The ancients believed that blood and bones were real, but craftsmen who specialize in this line know very well that this is a fake and deceptive thing. True or false depends not on blood, but on the ingenuity of craftsmen. They use this to deceive the ignorant masses and collect the black money of purposeful insiders.
So the real situation is that the same blood is compatible and the different blood is incompatible.