help with reverse genealogy

Bruce,

You haven’t given any dates which it makes it hard to advise you effectively. But for the aunt who moved to Belfast, have you found her grave? Who else is buried there? Some Belfast graveyards are on-line:

https://www.belfastcity.gov.uk/births-deaths-and-ceremonies/burial-records/search-for-a-burial-record

If the family was Catholic try Milltown graveyard. Their records are not on-line but if you ring the office they will tell you if they have a grave there. There may be a fee for getting the full details of who is in the grave.

Have you searched for her or her husband’s wills? They should be in PRONI. If more recent than about 1970 you would need to go into PRONI to look up the will calendars (index books) year by year. Or pay someone to do it for you. Obviously wills are likely to mention any children they had.

Have you searched the on-line newspaper archives for death notices? Often they say things like “Deeply regretted by son x , daughter in law Y in Liverpool, grandchildren in Australia” and so on. That can give you clues.

For the boy that you cannot trace after his birth, have you looked for a death for him? May have died young.

When people appear to have disappeared from Irish records it can be that they have moved to Scotland or England or further afield. Lots of people still leave Ireland for work elsewhere.

Search Ancestry and Wikitree in case somebody else has researched this family and knows a bit more than you do at present.