No, now that you mention it, I don't think they're married. Yet, you'll see in the linked quote below that the reporter refers to him as "stepfather." Also, he does have a very common name, so finding an RSO with that name might not be as significant as it would be if he had an unusual name.
This is what LE had to say about his polygraph:
Baums mother and the stepfather of the young girl Baum had been visiting just before she disappeared have both taken voluntary polygraph tests to aid the investigation.
They asked to be polygraphed so that we would be comfortable with what we were being told and we could move on to other things, Scott [Undersheriff] said. They did not want us to be wasting valuable time.
Scott said he was comfortable with their answers."
http://www.thedailyworld.com/articles/2009/07/02/local_news/doc4a4cf43c1b1dd881132403.txt
So . . . I'm not sure what he means exactly by "comfortable."
OT-- There are too many people in this case named Scott!