My long-awaited self-made Christmas present: the complete Gundam The Origin manga serie by Yoshikazu Yasuhiko! Hooray!
ANSWER: This story is open to any interpretation. It makes me happy when people try to find their own interpretation, instead of looking at mine.
Some readers suggested that Ybrids may represent animals, and their human features symbolize the fact that animals have a soul that is not different from that of humans (as it can feel pain, happiness, etc.). This is a perfectly fair and well-functioning explanation.
Actually I quite like this interpretation , even if it is not what I had in mind.
In my intentions Ybrids stand for a peculiar kind of men. In this story, Humans, Sub-humans, Soldiers, Nazys, Ybrids and even Animals, they all represent various types of humans.
The emperor of the title is Nearco the First, aka Egmont Zavijava CCV (205th), and the brave people who read this explanation sheet, will have no difficult in understanding what is going on here.
The queen loves white cats, she has 10 of them.
The big Goat, who later in the story will become the personal tutor of the young prince is not a Ybrid, but an "Antybrid". In fact, having a human-like body and a goat face, he is the opposite of an Ybrid.