Information on freereg, which you may already have.
Father Henry.
Tamar DONNITHORNE Baptism 08 Sep 1672 Cornwall St Gluvias : St Gluvias the Martyr : Parish Register
Also John DANNITHORNE 1671, Anne DONNYTHORNE 1674 (Mother also noted as Grace)
Jane DENYTHORNE 1677, Nicklas/Nicolas DONNYTHORNE 1682 (Burial 1683) (Henery & Grace noted), there may be others.
Looks likely that Henry was buried 1709 & Grace 1715 (No detail)
Honner DENITHORNERalph KENT Marriage 15 Jun 1700 Cornwall St Gluvias : St Gluvias the Martyr : Parish Register
Possible baptism. Father John
Ralfe K[EO]*NT Baptism 19 Aug 1669 Cornwall Perranzabuloe : St Piran : Parish Register
Brother John1672 & 1680
Tamar KENT Burial 26 Apr 1740 Cornwall St Gluvias : St Gluvias the Martyr : Parish Register
I note that Ralph & Tamar had several children, including Henry 1707/08 & Grace 1716, it’s possible the burial below might be Henry.
Son of Ralfe & Tamur
* KENT Burial 15 Oct 1708 Cornwall St Gluvias : St Gluvias the Martyr : Parish Register
My guess would be that this is all correct for Tamar/Honner despite her parents names not necessarily being in the English naming pattern, which was not followed by all. I do not see another marriage but not all married young, so 28 is not abnormal in my opinion.
Colin