Asteroid Mate by S. J. Talbot

When Squads from the Planet Relica visit alien worlds, it’s because those worlds are in danger. So when Commander Tausson Corwin comes to Earth to prepare the planet for evacuation, it’s Tierney Dawson, the President’s Chief of Staff, who is trying to coordinate the American role in the disaster response.
The Relicans help far off worlds — like Earth — who don’t have the technology to fully help themselves. But Commander Corwin’s culture dictates that this process is also how he is to find a mate. This ensures that Relican bloodlines exist throughout the Galaxy and save them from their own extinction.