Rightio! - here are the children of William Trewhela grouped together under each of three wives:-
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Elizabeth Tremellin1. Jane daughter of William Trewheela bp. 18th January 1755 Kenwyn and buried 16th March 1761 Kenwyn
2. Mary daughter of William Trewheeler bp. 8th November 1756 Kenwyn married Richard Soper at St Clement 19th July 1779 (10 children and Mary Soper buried Truro St Mary 17th November 1840)
3. John son of William Trewhela bp. 3rd September 1758 Kenwyn and buried 13th May 1828 Mylor married first Susanna Harvey at Budock 1786 married second Jane Trevena widow 1811 St Gluvias married third Jane Bond widow 1814 Falmouth (1815 Lent Assizes sentenced to 9 months imprisonment for Bigamy!)
4. William son of William Trewheler bp. 13th July 1760 Kenwyn and buried 10th August 1760 Kenwyn
5. Richard son of William Trewheeler bp. 18th October 1761 Kenwyn married Martha Snow at St Gluvia 24th July 1784 - descendants to Russia and New Zealand
6. Jane daughter of William Trewheeler bp. 10th October 1763 Kenwyn and buried 3rd September 1767 Kenwyn
7. William son of William Trewheller bp. privately 1st October 1765 Kenwyn - no further information
8. Betsy daughter of William Trewheeler bp. 4th July 1767 Kenwyn married Joseph Williams at Kenwyn 16th December 1792
9. James son of William Trewheeler bp. 23rd July 1769 Kenwyn and married Catherine Brown at Kenwyn 10th July 1794 - 3 children then James buried 25th November 1804 at Kenwyn. (Catherine then had illegitimate son Simon Tregunna Trewhela 1806 at Kenwyn
10. Jennifer daughter of William Trewheler bp. 2nd March 1772 Kenwyn and buried 3rd March 1772 Kenwyn
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Elizabeth James1. Jane daughter of William and Elizabeth Trewheler bp. 7th March 1775 Kenwyn and buried 29th October 1779 Kenwyn
2. Ann daughter of William and Elizabeth Trewhelar bp. 27th October 1776 Kenwyn and buried 20th March 1778 at Kenwyn
3. Charles son of William and Elizabeth Trewhelar bp. privately 10th August 1778 Kenwyn and buried 27th December 1840 Kenwyn 'of Truro Poor House age 62'
4. Ann daughter of William and Elizabeth Trewhalar bp. 6th August 1780 Kenwyn and buried 16th September 1780 Kenwyn
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Catherine Truscott1. Warne son of William and Cathrine Trewhelar bp. 21st May 1782 Kenwyn - married someone named Sarah - 1 known child Richard Thomas Trewheeler bp. Chatham, Kent 13th May 1804 - no further information
2. Jennifer daughter of Wm and Catharine Trewheler bp. 30th May 1784 Kenwyn married first Peter Tregunna Kenwyn 5th February 1803 and married second Samuel Truran Kenwyn 15th June 1810
3. Christian daughter of William and Catherine Trewhelar bp. 8th April 1787 Kenwyn married Peter Hancock Kenwyn 16th August 1813 - Christian buried 3rd May 1838 at St Day. (Christian had an illegitimate son Henry Trewhela bp. 11th June 1809 at Kenwyn. Henry married Jane Robins at St Day 21st December 1837 but no known children - he was buried at Bere Ferrars, Devon 2nd August 1854)
4. Francis son of William and Catharine Trewhelar bp. 26th December 1789 Kenwyn and buried 27th May 1798 Kenwyn
5. Henry Williams son of William Trewhelar bp. 8th October 1792 Kenwyn married Mary James 11th August 1833 at St Gluvias - no children. Henry Trewhelar of St Day age 65 buried 31st August 1856 at St Day
That should help fill in the gaps.
CT