I was looking at 1881 census - Ballachrink - where a John T of right age resides - seems to match marr of John T Cain + margt Jane Kelly (ticked some of initial boxes mentioned by Viv - Onchan, Kelly tho no Jurby connection) - however can't match Thos Cain + Margt Kinnish in 1881 census.

I believe this is Thos Caine & Mgt Kinnish

1881 Onchan
District Page Entry Last Name First Name Place Relation Condition Age Occupation Born Census For
01 05 024 CAIN Thomas Mount Murray Head Married 48 Ag Lab Michael Braddan
01 05 024 CAIN Margaret Mount Murray Wife Married 40 Ag Labs Wife Michael Braddan
01 05 024 CAIN John T Mount Murray Son 13 Scholar Braddan Braddan
01 05 024 CAIN James L Mount Murray Son 11 Scholar Braddan Braddan
01 05 024 CAIN Harriet Mount Murray Daughter 5 Scholar Braddan Braddan

I think this is John Thomas Caine and Mgt Jane ? Kelly can't find a marriage

1881 Onchan
Onchan CAIN John T. Ballachrink Head M 45 Farmer Of 61 Acres Employing 1 Labour Onchan IoM
Onchan CAIN Margaret Ballachrink Wife M 30 --- Santan IoM
Onchan CAIN John T. Ballachrink Son U 15 Farmers Son Onchan IoM
Onchan CAIN Alfred Wm. Ballachrink Son U 13 Scholar Onchan IoM
Onchan CAIN Agnes L. Ballachrink Daur U 11 Scholar Onchan IoM
Onchan CAIN Jessie Ballachrink Daur U 9 Scholar Onchan IoM
Onchan CLAGUE William Ballachrink Serv U 25 Farm Servant (In Door) Laxey IoM
Onchan SIMPSON Louisa Ballachrink Serv U 24 Domestic Serv Lonan IoM

I think Frances you are right that John TAUBMAN Caine ch 1867 Onchan is s/o the above John T & Mgt of Ballachrink
If this is right the gfa Wm Caine of Ballachrink died 1874 and has will CAINE, William 1874 Onc E 80 0106479

I don't see the will on the will index but I have it

William Cain Onchan 1874 #80 0106479:
This is the last will and testament of William Cain of Ashley House in the parish of Conchan.
I give and bequeath all my personal estate to my wife Catherine Cain
subject to the legacies following which are to be paid within twelve
months from the death of my said wife and not before viz - to my sons
John Thomas Cain, William Edward Cain and Alfred Cain a legacy of ten
pounds each to my grandchildren Margaret Emily Anderson, Joseph Anderson,
Daniel Anderson, Edward Anderson and William Cain Anderson the children
of my decease daugher Elizabeth late the wife of Daniel Anderson of the
town of Peel the sum of ten pounds each as legacies.
To my daughter Sarah now the wife of John Trimble of the town of
Liverpool a legacy of one hundred pounds.
To my daughter Harriet wife of William Callow a legacy of one hundred
pounds.
Lastly I nominate constitute and appoint my said wife Catherine Cain sole
executrix of this my will hereby revoking all former wills by me at any
time heretofore made.
In witness whereof I have hereunto subscribed my name this twenty third
day of May one thousand eight hundred seventy three (1873) William Cain
my x
Signed published and declared by the testator as and for his last will
and testament in presence of us who in his presence and at his request
and in presence of each other have hereunto subscribd our names as
witnesses. The same having been first read over to the testator when he
placed his cross mark thereto and direct his name to be signed for him.

W. Dickinson
T. Kneen
23 Oct 1874 - Catherine Cain widow and relict of Wm Cain sworn executrix
with pledges being John Quine of Balligee and John Thomas Cain of
Ballachrink in Onchan.
22 Feb 1883 John Trimble and Sarah Trimble received 100 pounds
Witnessed by Ellen Lawrenceson
12 Elan Street
Hugh Quarry
27 Feb 1883 - Daniel Anderson of Peel received ten pounds from John
Thomas Cain
Witnesses by Charles Coole
27 Feb 1883 - William Callow and Harriet Callow of Douglas received 100
lbs from John Thomas Cain
Witnessed by Charles Coole
27 Feb 1883 - Edward Anderson of Peel received from John Thomas Cain
executor of the will of the late William Cain of Ashley House in the
parish of Onchan the sum of ten pounds
Witnessed by Charles Coole.
27 Feb 1883 - Joseph Anderson of the town of Peel received 10 lbs.
27th Feb 1883 - Margaret Emily Anderson received from John Thomas Cain 10
lbs legacy.
28 Feb 1883 - Alfred Cain received 10 pounds legacy
Witnessed Joseph Heathcote No. 413 Cleggs Lane Little Hulton Lancashire
1 Nov 1884 - Willliam Cain Anderson of Peel Joiner received ten pounds
legacy.

Don't know what happened to wife Catherine Caine Caine who seems to be b1810 d/o Thos Caine/Mgt Cowin
Wm Caine was s/o Philip Caine & Catherine Colvin/Calvin

Onchan MI
Old Yard
L 10
Sacred to the memory of Philip Cain of Ballachrink in this parish
who departed this life 11th of March 1831 aged 68 years
also to the memory of Catharine Cain alias Colvin wife of the
above named who departed this life the 24th of April 1839
aged 70 years