Sorry, KK8, I wasn't clear enough.
What my "Rats" was about was that Thomas actually did marry pre-1837, i.e. before registration. That means no marriage certificate is available. The only record is in the parish marriages register, the transcription of which I linked to earlier:
http://www.cornwall-opc-database.org/search-database/more-info/?t=marriages&id=492250and it doesn't name parents.
The witnesses were John M? and Thomas G Hicks, which don't offer any clue either. Looking through the list on a search for all marriages in Kenwyn 1835-1837, e.g., Thomas G Hicks was apparently the parish clerk, since he witnessed dozens of marriages. For most, the other witness was a Margaret Courtice who signed with her mark. I don't see another witnessed by a John M, so he could have been a relation of some sort.
Spellings of surnames were still somewhat random in the early 1800s, and also it could depend on the predisposition of the person recording a name. One might guess that Clear was pronounced Clare at the time, or at least sounded like it in a local accent.
DNA testing has revealed that the surname of one of my ancestral male lines was Hoar, a surprise to me. That name, which is well known in both Cornwall and Devon, was spelled variously Hore, Hoar and Hoare, sometimes by the same people at different times, with different branches of what seems to be my particular Hoar clan mainly using one spelling or another in some cases. Then came modern times, especially in the US, when nobody remembered that the name was actually pronounced "Oar", and some individuals changed it, unilaterally, to things like Hoard and Orr.
So anyhow, you're stuck for evidence of Thomas's father, unless there is an actual record of his baptism in France that could be found somewhere ... which seems unlikely. Only one thought ... if Philip left a will it might have named his children ... and I don't really know about finding wills, myself.
Like I said -- DNA testing! If there is a direct male-line descendant of Thomas in both your family and Joobles', that would settle the question.
Just a general note that to order certificates, should you need any in future, always order directly from the GRO:
http://www.gro.gov.uk/gro/content/certificates/Any private intermediary will charge ripoff prices for no benefit.