Many years ago when I was trying to break down a genealogical brick wall in my family tree, I left a number of posts on an online forum that is arranged by surnames. Some of the posts paid results almost immediately as was the case I am specifically thinking about now and others take many years before someone discovers them and makes contact with me. When that happens, sometimes together we can solve the answer and sometimes we just exchange notes and a new friend/relative is made.
About a month ago, one of these posts that was answered years ago, yielded fruit in a different way. A researcher for a distant relative of mine posted a new question on that post and I made contact in an effort to answer her question. In this case, she was looking for information on the grandson of the common ancestor I share with the distant relative. I had some information on that person only because he happened to be related to one of my brick wall families and in trying to figure things out, I often traced lines down to distant cousins in hopes of producing new information.
We swapped information and in the process, I learned of another brick wall further down the tree. It is funny because that brick wall doesn't bother me in anyway but for my distant relative, it is a major brick wall. With my help, I was able to help peer beyond the brick wall in one direction but not another. In plain English, due to a probable out of wedlock birth and subsequent adoption, we may never be able to break down the wall completely. However, being male and the unknown person in question was along the paternal line, DNA may be the solution to at least give us a pretty good guess as to who the unknown person was and thus a way to peer behind the other side of the wall.
I've offered my help because darn it, I love a good mystery when it involved genealogy and one like this doesn't come along very often. Plus, we are related and that is what related people do. They help out their blood, even in this case if blood is very distant. I wish I could tell you more but due to the nature of the adoption and living descendants, I think it best to leave it to generalities. But I do encourage others to definitely leave comments or questions on these forums that even if they don't return results right away, they will definitely yield fruit years later when you least expect it.