Will there be a second installation where you meet the other siblings?
There are already 2 new stories:
Interea - this is a story about the moon tour mentioned in Adastra, so after Amicus become emperor and before the MC needs to return home . It fleshes out what happened on the tour and we have had 4 chapters of this story released so far. Please note that the releases are not happening as fast as in the past, but they are coming.
Khemia - this is the next main story in the series and takes place ~2.5 years after the MC returned to Earth. This story has had 2 chapters released but the author put it on hiatus and switched to Interea. This allowed him to handle a lot of backstory and character history for Khemia. Once Interea is done (10 chapters in all I believe), the author will be coming back to Khemia.