If you put both mother's an father's name in a text field with the names separated by a carriage return, you can then use this in a relationship to match by Father's name OR Mother's name.
You might try this calculation field for that purpose: List ( MotherName ; FatherName ) // Make sure text is selected as the return type.
I'm guessing that you are using this portal to search for siblings and half siblings. You may be interested in the "search" portals in this demo file:
It is very interesting the database you made. Thanks for the file and your help.
Actually, I am making a database for bird breaders. Birds, births, genealogy and customers, sales etc. I may expand the database into genetics, you know which bird should mate with which in order to get, lets say, a yellow canary!
You were very helpful, thanks again.