Not sure how you arrived at that conclusion as I can find just one record of a Stephen baptised to a John Hoskin (var.).
Anyway here is my list which I think differs substantially from yours.
John Hosking and Mary Uren married 22nd October 1772 at Lelant
1. Thomasine bp. 11th April 1773 Ludgvan and buried 2nd November 1790 Ludgvan age 17
2. Joan bp. 26th March 1775 Ludgvan married Thomas Williams at Gulval 12th November 1798
3. John bp. 4th May 1777 Ludgvan
4. Mary bp. 19th December 1779 Ludgvan
5. Stephen bp. 10th March 1782 Ludgvan
6. Grace bp. 4th July 1784 Ludgvan
7. Jennifer bp. 17th June 1787 Ludgvan (born 7th February 1787)
8. Thomasine bp. 24th January 1791 Ludgvan (born 10th December 1790) and buried 18th August 1791 Ludgvan age 9 months
9. Thomasine bp. 10th February 1793 Ludgvan (born 8th August 1792)
John Hoskin and Mary (nee Carbes) Uren widow married 5th June 1775 Ludgvan
1. John bp. 12th September 1775 Ludgvan (probably buried 12th November 1775 Ludgvan)
2. Mary bp. 12th September 1775 Ludgvan
3. William bp. 29th March 1778 Ludgvan
4. John bp. 1st September 1782 Ludgvan
Mary Carbess/Carbis/Carbence (etc.) was probably one of two baptisms at Ludgvan in 1741:-
11th July 1741 Ludgvan - John and Mary twin children of Reginald Carbuss baptised privately
25th January 1741/2 Ludgvan - Mary daughter of Francis Carbess baptised
In either case Mary would have been age about 48 or 49 by 1790 so it is highly unlikely she would have been the mother of those last two Thomasines. (I use age 48 as the cutoff for women to be having children back then and with a baptism you have to allow for the possibility that the child was more than a year old when baptised)
CT