A Time to Build: The Umea Bakearen, Book One

Wayne Freed always suspected that he didn't quite fit in. His suspicions were confirmed when he learned that he was not from Earth at all. His adoptive father told him that he was Umea Bakearen, a child whose existence had kept Earth out of a war which would surely mean its destruction.
Now, as an adult, he has settled into the life of an ambassador to the greater galactic community. He meets Ben Elan, the other Umea Bakearen with whom he switched places. Though initially jealous of one another, the two young men become fast friends. They vacation together, share stories of life on their respective planets, and even meet and marry twin sisters.
As they balance love and relationships with their duties as Umea Bakearen, they are renowned celebrities throughout the galaxy, except on Earth, where almost the entire population is blissfully unaware of the treaty that has prevented its destruction for over twenty years.
That is all about to change, however, because someone wants to keep Earth out of the Union, and they are willing to kill both of the Umea Bakearen to ensure it!