Connection made, yippee...! - the 81st Regiment of Foot was in Ireland at the relevant time and also the Channel Islands.
If Jethro, aged 40, left the army in 1832, what would he do? He doesn't seem to have returned to the UK as I can't find him in censuses.
Maybe he died leaving Mary free to marry William MARTIN [if they did actually marry]and produce their first daughter Mary MARTIN abt. 1836 in Cornwall.
I think it's his father Jethro senior's death in Somerset in 1845 [but no age given in the GRO]. Findmypast has 2 deaths listed in their index for that year for Jethro EASON - and I assumed it to be a duplication.
Jethro's 1832 discharge from the Army was due to ill health, so he may well have died shortly afterwards and not necessarily in England. He had been suffering from weakness of chest and general debility after a first attack of haemoptysis in Windsor, Nova Scotia in 1825, with further frequent attacks of haemoptysis thereafter.
The discharge hearing took place in Templemore, Ireland and Jethro was medically examined in Dublin on 17 Dec 1832.
The wives and children may have been based in Ireland or at the Guernsey garrison whilst the regiment was engaged overseas. One would not expect Jethro's family to have stayed in Guernsey after the 1832 discharge.
The 1845 death of a Jethro Eason corresponds to a burial in Merriott, Somerset on 17 May 1845 aged 79, so presumably the soldier's father.