Arai

Arais (singular: Arai) refers to humans who went to Rykol and their descendants.
Originally known as Rykolien Immigrants upon their return to Terra, the term was abbreviated to R.I., and the initials were turned into the word Arai. The term expanded to include any human who had been to Rykol or had Rykol-water in their blood. This means it covered humans that didn't return to Terra, as well as all descendants.
Once they realized that they would live for hundreds of years, the Arais began counting their generations and keeping track of their complete genealogy. While Arai initial growth was about the same as normal humans, they were often considered immature until they reached thirty years of age. However, they could continue to have children to very advanced ages.
The most prolific Arais were Rametin and Javiam from the spaceship Siberath, who had three hundred and eighty great-great-great-grandchildren at the time of On Alert. At that time, most Arai families could be traced six generations.

Fun note:

Tera, a member of the Alnevar crew, had a tendency to take abbreviations or multiple words and turn them into words of their own.
Hence...

• I'll Never (a slogan from the Information War) turned into Alnevar
• R.I. turned into Arai (and R.I.'s into Arais)