In 2001, I corresponded with a descendant of Margaret (Skillicorn) Cowin, Peter James Grant, who, I believe, still has a website (perhaps at Family Tree Maker?). You might contact him, to see if he has been able to go back further in any of these lines.
I think that Thomas Cowin was the son of Phillip and Margaret (Cowin) Cowin, but I haven't researched that family.
John Skillicorn, ďson of JohnĒ, was baptized at Lonan, October 18, 1765, and died there, November 3, 1813, age 47. He married, at Lonan, June 14, 1794, Margaret Corrin. She was the daughter of Philip and Ann (Gelling) Corrin, baptized at Lonan, March 10, 1765, and died there, March 30, 1837, age 76. She is the sister of Catherine Corrin, who married Philip Skillicorn.
John and Margaret Skillicorn lived at Ballacannell, Lonan.
John Skillicornís 1813 probate names his widow Margret, children Thomas; Margaret who married John Cowley; Ann, Jane, Elinor, and son John next of kin. Margaret is sworn executor, and supervisor of children under age. John Cowley, husband of Margaret Cowley als Skillicorn, acknowledges receipt of Margaretís legacy on January 26, 1822.
The will of Margaret Skillicorn, widow of Ballacannal, was dated February 20, 1837, and admitted to probate June 8, 1837. She leaves bequests to daughters Margaret, wife of John Cowley; Eleanor, wife of William Kewley; Jane, wife of John Clague; to son Thomas. Daughter Ann Skillicorn was named executrix.
Children of Margaret Corrin and John Skillicorn: baptized at Lonan
+ i. John Skillicorn was baptized December 18, 1796. He was lost at sea, age 35, December 10, 1831. He married, at Lonan, April 19, 1821, Ann Killip.
ii. Joseph Skillicorn was baptized February 2, 1799. He may be the Joseph Skillicorn who was buried at Lonan, June 10, 1825, but it seems likely that he died earlier, as he was not mentioned in his fatherís will, and the petition his mother Margaret states she is the mother of six children.
+ iii. Margaret Skillicorn was born about 1799, and died at Lonan, August 29, 1843, age 44. She married, at Lonan, March 11, 1820, John Cowley. He was born about 1794, and died at Lonan, August 18, 1878, age 84. He was perhaps the son of Thomas and Margaret (_____) Cowley. He married second, at Lonan, July 31, 1845, Margaret Cannell, widow of Thomas Kneale. She was born in Onchan, about 1808.
+ iv. Thomas Skillicorn was baptized September 19, 1802. He is mentioned in his father's 1813 will, and his mother's 1837 will. He is probably the Thomas Skillicorn who married at Lonan, March 19, 1831, Isabella Cowin.
v. Ann Skillicorn was baptized December 23, 1804. She was the executrix of her motherís 1837 estate. She may be the Ann Skillicorn who married at Lonan, July 29, 1837, Ewan Kissack of Maughold. No parents were named in the marriage record. Ewan Kissackís wife Ann died in 1886, age 71. (From her age at death, and from census, it seems likely Ann Kissack was born 1805-1808.)
+ vi. Jane Skillicorn was baptized May 17, 1807. She married, at Lonan, June 12, 1835, John Clague. She is mentioned in her father's 1813 will and in her mother's 1837 will.
+ vii. Elinor Skillicorn was baptized October 13, 1811, and died at Lonan, August 25, 1864, age 73. She married, at Lonan, December 4, 1830, William Kewley. He was born about 1806, and died July 8, 1882, age 76.
John Skillicorn (John-Margt Corrin, John- ) was baptized at Lonan, December 18, 1796. He was lost at sea, age 35, December 10, 1831. He married, at Lonan, April 19, 1821, Ann Killip.
Ann was the daughter of William and Jane (Kewley) Killip, baptized at Lonan, December 18, 1796. Annís identity is confirmed by the joint will of her parents, dated October 22, 1831, and admitted to probate June 10, 1836. William Killip, with the joint consent of his wife Jane Killip, alias Kewley, leaves a bequest of 5 £ British to his daughter Ann, wife of John Skillicorn. Ann Skillicorn died at Lonan, December 21, 1871, and was buried December 24, 1871.
Ann Skillicornís will was dated June 21, 1867. She leaves bequests to her son John; to granddaughters Ann and isabella Crain £10 each when they reach to age of 21 years; to daughters Eleanor wife of James Skillicorn and Jane wife of John Kewley who are in America; to daughter Elizabeth wife of Thomas Kelly of Lonan and granddaughter Jane Kelly. Her brother John Killip of Ballacollister is to be executor.
She did not leave a bequest to Margaret, but perhaps Margaret had been given money to emigrate to Australia?
Annís sister Margaret married James Skillicorn, son of Philip and Judith (Killey) Skillicorn.
Ann Killip had married first, at Lonan, November 16, 1809, Thomas Cain of Kirk Onchan. His noncuperative will was admitted to probate at Douglas, July 3, 1813.
Good luck with your research. If you have any additions or corrections to this information, I would appreciate having them.