Just concentrate on the top text and image. He's telling us that the two children are himself and a little boy he names David...and it's 1968. 
Now we have two children he once again describes as himself and David, and it's now 1971, there years later.
NO WAY! No way can anyone help you identify any of the children on the pages you posted. I doubt if you would find anyone who would try...unless they understood just what Mark is up to and why.
correction:
there years should be three years...
Look at the features & not at the specific dates.
Also, these are family pictures, and one can see the age progression of the boys.
In my original post, and my repost here, I put names to them for ease of reference.
If one of the boys looks different, then we can give him a different name.
But again, look at the faces and skin tones; “forensic facial features” analysis.
Ping to this repost:
http://www.freerepublic.com/focus/news/3505072/posts?page=603#603