Col
As I am going with the theory he may have been married before his Marriage to Cassie.

There is a John William Teare Ch June 19, 1850 to William , a Weaver, and Mary Fargher , in Andres , residence Dhowin.
He appears to marry Eleanor Shimmin December 24 , 1871 ,
Kirk German, he was a Joiner.
They have children Eleanor Mary , Jan 22, 1872 and William Alfred Jun 20, 1873 , who dies Jun 21, 1874.
I do not have access to 1881 census IOM , I cannot find marriage or death for Eleanor Mary or obvious death of John and Eleanor.
Can you check to see if they were still on the Isle in 1881 ?
Cheers
David