I managed to get myself a slot at PRONI this week and despite the utter lack of carparking in the area currently succeeded in entering the building.
I was able to look at a large map from the late 1780s, showing the estate of a Mr Johnston in the Drumbanagher area. It shows locations of houses and field boundaries and lists the tenants in various townlands.
Essentially, it confirms a negative: no Gibsons or Hanlons were living in the area at that time.
I was able to look at the microfilms for St Patrick’s Church, Ballymacarett, focussing on weddings up to 1900 or so. Again, this was a negative: I could not find the marriage of Mary Smith to Robert James Brown. I had hoped that they had married there and just not registered the wedding with the civil authorities.
Another possibility is that this is what happened but at another church in Belfast.
The St Luke’s Killevy Church did have some references to Browns but I cannot link them to either of our branches at present.