Hi Tim

Further to Jean's find of possible brother find, the following should confirm Thomas and Catherine Quirk as parents:
Checked sister of Isabella, Catherine christened Dec 31, 1815 ( checked and confirmed with hand written records).
Found a marriage of Catherine Kelley to Decator Powell March 1, 1839 Aid township , Lawrence county, Ohio.
They had 11 children with some strange names, but included an Isabelle also listed as Isabella.
This Catherine Kelley Powell died Arabia, Lawrence, Ohio and is buried Myrtle Tree Cemetery , and from Find a Grave she is shown born Isle of Man December 25, 1816 ( is wrong , must be 1815).
From Catherine's marriage this assumes the family must have been in Ohio as early as 1839, and as Isabella would have been only 10 to 12 , looked for the deaths of Thomas and Catherine.
BOTH FROM FINDAGRAVE:
1847 June 28, at Mentor Municipal Cemetery , Lake County Ohio, Thomas Kelly , no DOB, but born isle of Man.
1850 March 13, Thompson Cemetery Lawrence County , Catherine Kelly , shown as Wife Of Thomas, birth details unknown. You can see a photo , but not too clear, another notation " Only readable stone in Cemetery".
Frances has a CD and part online "amanxnotebook" , it includes a listing of people on the 1880 U.S. Census that gave IOM as place of birth , about 3 to 4 thousand. 670 in Oh , 504 Ill only a few in NE. Catherine Powell is on the list born circa 1816, John Kelly also there born circa 1815, but no Isabella Bickel.
What I find strange is every where I go Thomas Kelly's wife is shown as Kirk , not Quirk as it should be. All birth details on the LDS IGI are shown correctly , so is Kirk shown on Death Certificates ? Have you tried to get Isabella's death Certificate ?

Cheers
David