(willing to adjust to fit the reading, but need receipts and proof)
Chiss are a highly advanced society that had to adapt to a horrendous life on Csilla. They live underground.
Csilla above ground is like the RL planet Neptune where methane freezes. Possibly through the rock on Csilla, when the methane thaws, it can for sufficient amounts of water that is potable. That is why the Chiss who are thought to be space-faring chose the planet.
Because they’re technologically advance, they no longer have children by birth. Their lifestyle is like “Brave New World” and everyone is out of a petri dish. It is safer and cleaner. That is not to say they don’t have sex, they do, they just do it for fun and no children.
The only way a woman can have a child is to be off-world remote rural planet – like in the book, Brave New World. The only way a man could impregnate a woman is to off-world remote rural planet.
The Chiss Ascendancy and the Aristocra do not believe in cross-species fertilization.
There are generally no such thing as husband/wife and families in the sense of blood. Families are in the sense of units that grow up together. Sorta like the clones in the Clone Wars and sorta like the First Order, but not exactly. Slightly different.
Yes, this goes against the 2001 Alien Anthology by WOTC, but this would be an upgrade and a change from the SWEU establishment.
Say some disease happens in long hibernation flights, and an entire family can be destroyed genetically by infectious agents. Therefore, in vitro in a sterile environment is more advantageous, than natural reproduction and birth.
All this to say that while Mitth’raw’nuruodo and Mitth’ras’safis were born to the same parents (same mother and father) as commoners. Thrawn has a brother named Thrass in Star Wars Legends, namely Outbound Flight http://bit.ly/ThrawnStarWars