I note Thomas Bowen was of Crunwear at his mrge to Mary John of Amroth in 1815 so, I trust I have not given this info previous, but from my index of all names and relationships in all wills proven at Crunwear at the E.C.C. of St David’s I note the will of Henry John a yeoman of Long Parks Crunwear reference nbr 1822/23 which makes reference to his daughter Mary John, Henry’s wife is Sarah with two sons Thomas & Henry and a further three daughters Ann, Genat (I suggest this is Janet) and Maretta. The will was wittnessed by Thomas Dalton Vicar of Crunwear and his possible brother John Dalton.
The only reference I can currently find to Martha Bowen is a baptism in Tenby in 1819 and at Redberth in 1822.
As you are probably aware Isaac Bowen married Elizabeth Nash at St Issells in 1787, which would suggest your theory is well on the right lines.
I note the baptism entries for the name of Mary John at Amroth 1815(Prob buried 1815), Amroth 1816, Tenby 1816, St Issells 1817(Prob buried 1818) and Begelly 1818. this would appear to suggest your Mary baptised 1816, would this fit to your known research?
I’m afraid to take your requirements further, the query will need to be added to my “to do” list for a future visit to Pembs R.O., however I am currently tied up converting half my garage into a useable Computor/Study/Research Room, so will not be at the R.O. anytime very soon. (Perhaps next week).
Hope you can await my visit and I trust the above is of some little assistance.