Leigh Brackett’s standalone space adventure The Starmen of Llyrdis was first published in 1952, under the title The Starmen.
Perpetually out of step with the world, Michael Trehearne has travelled to Brittany in search of his family roots. When he glimpses a face much like his own, he is convinced he has come to the right place. He is both right and wrong: some of his kin are at hand but they are only visiting Brittany. Their true home is far from France.
Light years away, in fact.
Spoiler warnings, for this and for the unrelated The Long Tomorrow.