Considering that there was no affiliation or loyalty between these two mares before the older mare gave birth this year, it is a wonder that the young paint mare has attached herself the the older mare and foal. The paint mare loyally follows the other mare and has taken to caring for the foal with devotion.
The above images shows the “God Mother” mare grooming her adopted foal while the actual mother grazes.
The image below shows the trio with the herd stallion. This is the first time I have observed this stallion interacting with a herd foal.