I was wondering if you'd see a family resemblance. Good luck with your search for William I have my fingers crossed for you!
Briefly re the Nixon side:
James Nixon 1766-1850: Farmer Tullynadall, townland in Inishmacsaint, Co Fermanagh
married Jane Acheson 1771-1855 ( our great great great grandparents)
They had 8 children
1. MARY 1795-1812
2. JANE baptised 1801?
3. ANNE baptised 1801?
4. DOROTHY 1804-1886
5. HUGH 1806-1882 Married to ISABELLA ACHESON 1820-1887 (our great great grandparents)
6. JAMES 1808-1891
7. NATHANIEL 1810-1893
8. ISABELLA 1811-1875
- Hugh and Isabella Nixon had 8 children
1. WILLIAM 1842
2. JAMES
3. REBECCA 06/08/1846 - 1914
4. MARY JANE 1848
5. ANNABELLA 11/08/1854
6. GEORGE 1857-1866
7. ELIZA ELLEN 07/09/1856 - 13/04/1907 m EDWIN JOHN JOHNSTON (our great grandparents)
8. WILLIAM HUGH 1862
Eliza and Edwin Johnston had 6 children ( our grandparents)
1. WILLIAM ROBERT 06/11/1889 - 09/02/1940
2. ELIZABETH 29/10/1890
3. EDWIN JAMES 05/03/1892 - 25/01/1948
4. ISABELLA DOROTHEA MARY (May) 16/05/1893 - 13/08/1976 m. CHARLES ANDERSON MILLER
5. SAMUEL HUGH 04/04/1894 -19/01/1933
6. REBECCA ELLEN 10/01/1896 - 18/10/1941
May & Charles ( Charlie) Miller had 6 children
1. SARAH 12/10/2014 -09/11/1994
2. JAMES 15/06/1915 -11/04/1986
3. ELIZABETH ELLEN 15/06/1917 -27/09/2005
4. JANE 04/07/1923 -07/01/1998
5. WILLIAM MOORE 15/08/1925 -02/03/1990
6. CHARLES ANDERSON 01/04/1929 ( alive) m. MARGARET MURPHY 1929-1994
Still checking through paperwork and certificates, apologies if errors!!
will amend asap