There would appear to be field options specified for the _fk field that should be removed.
Either it is set to auto-enter a serial number or you have specified a unique values validation option.
Whichever is the cause here, you need to remove them.
In the options on both the parent and child field I assigned a unique serial number and prohibit modification. I unchecked those two items in options for the child field and it worked with crows feet showing up on the child side. This makes sense looking back but I'm just learning.
Thank you very much