Import to a Related Field

You would need to be more specific with examples of relationships and what the Key field is of the tables involved, but if for example the Key field of the parent record is [Record ID#] then you would need to find a way to manipulate excel to do some kind of Vlookup to know that value is. or else have a Pipeline run to do a search and populate that field.

We would need to have a specific example to work with to help you more we would have to know how some kind of algorithm or rule would be to know what the proper parent is supposed to be  .