Family Historian User Group

I'm using a gedcom from ancestry.com as the original source for the project. Now if I make a chanage on ancestry.com and merge that gedcom with my project I get two new fields for children:
FREL Natural
MREL Natural

I've made no changes to these records yet these fields appear. Does anyone know what they are?
Thnaks

ID:6241

I suspect this is the Ancestry customised version of the GEDCOM 5.5 standard PEDI pedigree tag, that allows Parent - Child relationships to be defined for cases such as Adopted, Fostered, illegitimate, etc.
These can be set differently for each parent.

My guess is that FREL and MREL are Father & Mother RELationships, and Natural means natural birth parent.