Hello there. Interested to see you use the phrase 'common law wife' - It was never possible, either before or after the 1753 Marriage Act, to enter into any kind of 'informal' marriage arrangement that gave a couple any rights whatsoever in law, other than through a legal marriage before an Anglican clergyman (before 1837) or in addition before a civil registrar or registered religious officiant (after 1837). Are you sure they didn't marry? Was Thomas for example already married to someone else? I'd highly recommend Rebecca Probert's "Marriage Law for Genealogists", on Amazon, to get a really good idea of the possible explanations of their living arrangements - a real eye opener.
