Toughie Olivia,
Normally a predecessor could relate such tasks, but since the presence of a predecessor "taints" the data, it's a Catch-22.
Instead, one approach would be to add a custom data parameter (e.g. a checkbox called "Sync Task") to each Task in all such pairs on a Project (and if you like the approach well enough, even on your Templates), and optionally, a second calculated text parameter (e.g. called "Sync Task Name") with a formula of REPLACE(Name,"AUTOCALC:",""), then filter for Sync Task true, order by Sync Task Name, and view the Planned Start Date of each for easy grid-editing to ensure they match.
Regards,
Doug