In the parent record create a new calculation field
List (related_table::field_name); "<pillcrow>"; ", ")
FYI, the pillcrow is the carriage return character.
Substitute ( List ( related::field ) ; "¶" ; ", " )
List() gives you a return-delimited list of a related set of records (by field).
The Substitute converts the returns to comma+space. If there are only two 'values', there will only be one return in the List to convert.
Thank you both very much!