Just stumled over this issue. I do youth work and would like to add kids’“mother” -and “father”'s names to their contact. However, as discussed above, there is no “correct” translation from android to vcard which causes to become both a “parent” relation.
Here a test, how the android relation do resolve:
FN:Relationtest
N:;Relationtest;;;
RELATED;TYPE=co-worker;VALUE=text:Assistant
RELATED;TYPE=sibling;VALUE=text:Brother
RELATED;TYPE=child;VALUE=text:Child
RELATED;TYPE=spouse;VALUE=text:Domestic Partner
RELATED;TYPE=parent;VALUE=text:Father
RELATED;TYPE=friend;VALUE=text:Friend
RELATED;TYPE=co-worker;VALUE=text:Manager
RELATED;TYPE=parent;VALUE=text:Mother
RELATED;TYPE=parent;VALUE=text:Parent
RELATED;TYPE=spouse;VALUE=text:Partner
RELATED;VALUE=text:Referred by
RELATED;TYPE=kin;VALUE=text:Relative
RELATED;TYPE=sibling;VALUE=text:Sister
RELATED;TYPE=spouse;VALUE=text:Spouse
REV:20200511T200233Z
END:VCARD
Why can’t you just make unclear relation type mapping a custom one, these way the data would actually not be changed with synchronisation which took me quite a time to find out. I always wondered, why these relation aren’t the same anymore on nextcloud after synchronisation.