In the second half of the 19th century there was a worldwide influenza pandemic.
The very high mortality rate created many orphans.Could Katheryna have been one of thoseorphans?There was no orphanage system in Galicia. DidAnna and Lucas die, leaving the very young Katheryna w/her uncle and Marya?
As an adult, she chose to name Hryhorij and Marya as Grandparents of her children.It could be that Hryhorij and Marya were loving and the only parents Katheryna knew.
My scenario is not all that far-fetched for the time frame.
Ernie, consider taking a closer lookat the death records for the ten yrs post Katheryna's birth.