One thing that seems to jump out is that the first boy was kidnapped at age 11. The next boy was kidnapped at age 11. I wonder if there were other boys who were kidnapped at age 11 by this guy, and we have yet to learn who they are - or were.
A distinct possibility.
The missing boy, (1991) they are trying to link to Devlin now, was eleven when he disappeared and lived about the same distance as these boys from Devlin's home.