Hi again
Yes, it does, although 21 was the legal age of majority so 18 wouldn't make any difference really.
I had another look last night and couldn't satisfy myself that I was looking at the right people! The 1861 census for this area is badly damaged, with some parts missing but that doesn't explain all the omissions.
I did wonder whether there was a second marriage in there somewhere ...
Confusing and probably needs a through look, which I haven't yet had time for.
A

Edit: In Lower Monk St in 1881 is an Ann MORGAN, an unmarried grocer of 54 and her niece Edith JONES aged 8 and born Abergavenny. Just those two! Sadly no number for the house!
Note that one of the witnesses was a JONES - but don't hold your breath for my proving a connection!