Deb from Smiths Official DNA Project, you're a member of course of the project (http://www.smithsworldwide.org)here- In order to try to chase down when what's called a Non Parental Event occurred, you'd need to see if you can find a direct line male descendant from each one of William's sons. For example, starting with William Jr, he had, if I'm reading one of the trees correctly, at least 3 sons. Seeing if a direct descendant matches your husband would tell you whether the NPE happened before or after that generation. The second thing you can do is list out the census records where your family went and see if there were any Delongs at any time in the same county. I don't have your full line of descent but if you will email me (email@example.com) I'll take a look at the census and see if anything obvious pops up.