A young man and a young woman work together in an office setting. They are attracted to each other; they date, get romantically and sexually involved. One day, he notices on her desk a photograph of one of her parents and recognizes it as one of his ownparents. further investigation reveals that the two are siblings separated when they were very young - and neither was aware of having a sibling. I do not recall what they did when they made the unwelcome discovery. I do not recall the author or the title of the story. I also am not absolutely certain of all the details i've provided, but it is what I remember. the story is likely at least 10 years old, maybe older. Any help appreciated