This is an update on these lines.
I went to the Court House in Indiana, PA on Friday, in an attempt to find out more about Abarilla Parrish McGinity, her husband James McGinity, and their son-in-law, Joseph Parrish. In the end I walked away with tax records spanning approximately 1808 - 1834.
It's worth noting Joseph Parrish does not appear in the records until 1826 in Blacklick, Indiana, PA. Where was he before this? He would have been roughly 33 at this point, and should have been well established on his own. Little is known however of his life prior to this time. The only other records are the 1800 census where he is likely in the household of a John Parrish in Alleghany Twp, Huntingdon, PA (aged 0-10), and then in the household of a J. Parish in Springfield, Huntingdon, PA in the 1810 census (aged 16-25).
It's also possible he was one of the Joseph Parrish's near Joshua in the tax records. Though that is highly uncertain and contentious.
Essentially what we have here is that James and Abarilla Parrish McGinity lived in Centre Twp, Indiana, PA from at least 1808-1815 at which point they moved to Blacklick, Indiana, PA. This is approximately 15 miles from Loretto, where Prince Gallitzin was practicing and Joshua Parrish worshiping.
A rather interesting piece came from this research. It was discovered that from 1816 - 1822, James McGinity's children were listed as "poor children of the township". What I've learned is that this means they were aged between 5 and 12 who were unable to pay for school, so the township paid for their schooling.
From family lore we know at least one daughter had worked for a family in the area. Now it seems likely it was certainly for economic reasons. Is it possible another daughter, Margaret, was placed with family due to her family's economic conditions? If so it could well explain why Margaret McGinity was baptized by Prince Gallitzin in 1823 at the age of 17 and why her godfather was John Parrish, son of Joshua Parrish.
Of course this is just another piece to the puzzle, however I think we're getting very close to the point where we can say with some certainty that Joshua and Abarilla were indeed related, and closely. The question still remains however, how were they related?
Based on their birth years, Joshua in 1770, Abarilla sometime between 1772 - 1780, siblings seems highly likely. However it is certainly possible they are related in another way. Possibly uncle/niece or cousins.
Finally I felt I should wrap up who Joseph Parrish is in case it was missed elsewhere. Joseph Parrish married Elizabeth McGinity, daughter of Abarilla Parrish and James McGinity. Supposedly he was Elizabeth's uncle. If so that would mean Abarilla's father was likely John Parrish.