The Terrans had been dismayed when they discovered they weren't the first to colonize Bright Skies. Though the Firstcomers were humanoids, they were so very different--taller and bulkier with such flexible hands, and their hair was impossible! Patterns that randomly combined colors and then ran in different directions. Sure, some of the women--and men--were intrigued by that, but both parties kept their distance until disagreements arose about which lands were available. The Firstcomers naturally were sure that they had first choice, and, by the way, the planet's name was Tortun, but humans being humans, there was escalating strife until a Terran killed a Firstcomer.
After the ensuing panic, the Firstcomers came up with a plan to make peace at least possible for coming generations. All must live together one way or another--in communities and/or in families. With their skill in advanced technology and genetic engineering, they could interbreed. The majority of Terrans refused, but some for various reasons, saw it as a possible solution and volunteered. There were even some matches based on mutual esteem and love.