You can force a different version of your model into memory, which will allow you to review parent/child references. Here's the simplest way:

If you select the "Commands and Settings" icon (the little down arrow at the far right), and check "All versions", Pro/E will let you retrieve a specific version of your file. Usually, all you need to do is pick the previous version, and Pro/E will give you the old "Version X of model XXXXX is already in memory. Please enter a replacement name" message and suggest "PRT0001" as a default. Choose any name you want and you can use that model for reference, especially handy if you need to investigate parent/child references during a re-route.