this is getting to be a habit - you need to check different records as just matching names leads to wasted effort - there are 4 (at least) Henry/Harry Lowey's dying in the 1730-1736 time frame - the 1731 is/was Isabel's spouse (hence the posthumous in 1732 + her remarriage in 1732 - as you suggest 1697 as birth year more children could be expected and in fact did arrive)

Harry senr would appear to pre decease henry junr by 1 month - thus Henry junr's eldest son would be heir at law tho probably too young to manage a farm - as I presume you have looked at the burial reg you would know that three Henries were of Linguaig as was Cath (d 1752 noted as widow) (the 1733 Henry was a child of Henry tho no place given) - the Lowey family held Lingague until at least well into the 1950s judging from the burial reg