The best way I have found to accomplish this is to use the append tool in pro but change the receiving field for the globalID to a GUID and check preserve the globalID, see post https://community.esri.com/ideas/13150. This way the the GUID field should now match the parentglobalid field in the related record.
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Hi Joshua, I am trying to use your script and I keep getting a runtime error on line 30. Also, I am new to python, what parts of the code do I need to change in order to so it works with my feature class.
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