I think we can rule out the marriage we have for John Jones, son o fEvan Jones, Farmer. The reason for this is that I have found them on the 1841 census and it shows:
Tyn Rhyn, Llangystennin.
Evan Jones, age 60, Farmer, born in same county.
Elizabeth Jones, age 60, born in same county.
John Jones, age 20, born in same county.
Jane Jones, age 20, F.S., born in same county.
Even allowing for the rounding down/up for the age of John, he was born too late for our person if we use the age he gives in the census returns.
There is an extract of what purports to be a death certificate for him on Ancestry. This shows he died age 47, of Gastro Enteric Fever. Informant Robert Jones, of Bryn y Gwynt, Eglwys Rhos.
The same Family Tree has a report of the birth certificate for Pierce Jones. It shows he was born on 3 November 1850, abode: Tan y Wal. Father: John Jones, labourer. Mother Elizabeth Jones formerly Williams. Mother marked information with her x mark.
The mystery continues....
Helig