Hello Patricia
A search of the NSW BDM Index shows a Joseph Minch marrying Mary Dowling in 1855 19/101 RC East Maitland/West Maitland. There is only 1 child (no name or sex) registered to a Joseph & Mary Minch-3182 121B
The only marriage I can find for Mary Minch that fits the time frame is to William Rigney in 1876 Gunnedah.
Ann