In most societies Hybrids might be looked down upon, out casts, and shunned yet one of the most totalitarian Empires in the known history of the universe is the exception. Hybrids are not treated just like any other citizen they are also encouraged by society at large.
Now this may seem both strange and rather hypocritical of a largely conservative and traditionalist Empire and really when you boil it down it both is and isn't. Within the Empire the tenets of Peace, Order, and Law (Also translated to Prosperity, Conformity, and Security) dictate that conformity must be part of every day life in the Empire this comes down to dress, language, and also blood. Inter species mixing is encouraged by the Empire as in their mind it will, down the line, establish a sense of community and acceptance in the larger Empire. This process in encouraged so much that over generations entire species have become part of the larger Rin genome and are almost identical with pure blooded Rin.
Now while the Rin see this as a good idea to practice it is not always accepted by all pure blooded Rin. Some lines of legitimate pure bloods still exist and by law are considered 'Princeps' (Rather high on the social ladder) and most Rin, Hybrids, and so on are expected to and tend to respect such individuals. Although this trend of pure bloods are slowly dying out over the generations and eventually hybrids will make up all Rin and the majority of the Empire at large.
Now if you are asking why the Rin can seem to breed with everyone, that is not the case. Some species are not comparable with the Rin at all (They are still accepted as citizens, but tend to be of lower standing and called the 'Tainted Bloods'). Most species within the Vigro super cluster, however, The Rin can procreate with. This is due to most sharing a common creator in the Angels of old.
Hybrids tend to take all sorts of forms. Normally what differs them from pure blooded Rin is the shape and exact charismatics of their bodies and most importantly their color. Rin Hybrids come in all sorts of fascinating and exotic colors a trait both adored and cherished by Rin of all classes. The most common/populous Hybrids are as follows:
- Forge Rin are Rin that descend from the Supellex peoples. They have yellow to light orange skin tones with facial and body markings coming in tones of white, pink, and light reds.
- Stellar Born are Rin descended from a species of nomads known as the 'Navigators' long ago assimilated into the Empire. They tend to be of yellow skin tone with white to light blue markings. They also tend to have tall and slender bodies due to low gravity upon the many void ships in the Empire. Stellar Rin due to their nomadic origins are spread all across the Empire and universe at large.
- Cordillera Rin are Rin descended for the Gigantis species and Rin colonist upon their homeworld. They are Rin of large build and tend to be muscle bound. They are common within the military, police forces, and under worlds.
Many other types exist like: Red, Purple, Green, and many other shades of Rin as well as all sorts of exotic types and builds. The only types of Hybrids frowned upon are those of none humanoid forms or of rather 'deformed' appearance by Rin standards.