Hi from me too Cath,
Just an observation here.
Mary Jane (nee DONOVAN) and her husbad were into what was considered then, advancing years.
They are unlikely to have reached out to a stranger to adopt a baby boy.
To my thinking the mother of the child is likely to be one of the daughters born in the 1870's.
Mother Mary has stepped in to the rescue! It is a well known story.

I have no evidence to support this, just conjecture.
Sue