Hi Val

Luckily there weren't many Duggans around in the south of the island at this time. Here's a possible set of parents and siblings for Thomas, copied from the IGI. The extracted entries are:
Richard 1792, William 1794, "Duggan no christian name" 1796, and Elizabeth 1799.
The rest are patron submissions:

Results for: Any Event, 1775 - 1815, Isle of Man, British Isles
Father: James Duggan, Mother: Margaret Callow
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International Genealogical Index / British Isles - 8
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1. ELIZTH DUGGAN - International Genealogical Index
Gender: Female Christening: About 02 JUN 1799 Malew, Isle Of Man, England

2. THOMAS DUGGAN - International Genealogical Index
Gender: Male Christening: 16 OCT 1796 Malew, Isle Of Man, England

3. JOHN DUGGAN - International Genealogical Index
Gender: Male Christening: 18 MAY 1805 Malew, Isle Of Man, England

4. DUGGAN - International Genealogical Index
Gender: Male Christening: DEC 1796 Malew, Isle Of Man, England

5. ANN DUGGAN - International Genealogical Index
Gender: Female Christening: 17 JAN 1802 Malew, Isle Of Man, England

6. WILLIAM DUGGAN - International Genealogical Index
Gender: Male Christening: 10 AUG 1793 Malew, Isle Of Man, England

7. WM DUGGIN - International Genealogical Index
Gender: Male Christening: 10 AUG 1794 Malew, Isle Of Man, England

8. RICHD DUGGAN - International Genealogical Index
Gender: Male Christening: 18 NOV 1792 Malew, Isle Of Man, England

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In 1841, there's a Richard Duggan who married a Jane Cubbon 17 Jan 1818 Arb (extracted) who is probably the one below. so at least one of these Malew-born children settled in Arbory:

Arbory district 3, page 9
Ballaglonney
Richard Duggan 50 weaver
Jane 50
Thomas 15
John 12
William 10
Margaret 7
James 4

Following your Thomas and Margaret through the 1841, 1851 and 1861 censuses, Margaret is widowed between 1851 and 1861.

This burial could be of your Thomas:

DUGGAN, Thomas 62 Arb 28 Jan 1857

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This might be Thomas's father, husband of Margaret Callow:
DUGGAN, James 77 Mal 6 Mar 1839

This might be Thomas's mother, possibly Margaret nee Callow, wife of James:
DUGGAN, Margaret 89 Arb 22 Jul 1854

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This might be Thomas's wife, Margaret nee Callow:

DUGGAN, Margaret 84 Arb 18 Sep 1886

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This one could be Jane nee Cubbon, wife of Richard:
DUGGAN, Jane 72 Arb 19 May 1875

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This might be Richard, Jane Cubbon's husband:
DUGGAN, Richard 73 Mal 25 Jul 1865

So, all speculative at this stage, but worth following up.

Please could some kind person see if there are MIs for any of these burials ?

Jean C