I have contacted several relevant places to date without success. I have telephoned Bishop Auckland Registra and Durham as well as the archives there all without success.
Both Bishop Auckland and Durham and Stockton registras' all report no Thomas or John Kavanagh of any spelling for those dates.
This is definitely a mystery case. In once census record Thomas is said to have been born in Wrexham then in Spennymoor in the net census, I cannot find him in either after telephoning, e-mailing and writing to the relevant places - hence my confusion. This is why I was hoping to find John but again no luck.
I am beginning to think only an expert can solve this one as no one has been able to so far but it does prove an interesting case. Shame Miss Marple isn't around now or Jessica Fletcher, I sure could use their help.