In case bluegenes does see stessy's post think I can identify his parents (even though can't find his baptism).
A John Dennis married a Drusilla Kent 15/11/1824 St. Columb, Major (both of that parish).
Elizabeth Mary Dennis bp.25/1/1825 St. Columb, dau. of John Dennis (tailor) and Drusilla.
They next appear in London:
Drusilla Thomson Dennis b.7/1/1830, bp.28/2/1830 St. James, Westminster, dau. of John Dennis (tailor) and Drusilla.
9 months later Drusilla Dennis, 26, of St. James, buried 14/11/1830 St. George Hanover Square.
So John juniors birth would have between those of his 2 sisters, When his wife died John senior was left with a 5 year old, a 4 year old (John) and a 10 month old baby. By 1841 eldest daughter Elizabeth is back in St. Columb living with her maternal grandparents, Robert and Mary Kent but don't know what became of John Dennis senior, or where John junior, and dau. Drusilla were.
Drusilla Kent bp.18/11/1804 St. Columb, dau. of Robert and Mary
John Dennis bp.6/1/1805 St. Columb, son of James and Elizabeth.
Annette