Sheila Mary, You will have to take this for what it might be worth. I have no way of telling if I have anything correct.
It is possible that Richard Boylan, John's father, might have been dead by 1823. He certainly is not holding land in the Ireland Tithes, although these records for Boylan appear to date from 1826 to 1834. As John has married, according to your own information by 1812, then Richard ( his father) is likely to have been born around 1760 and John around 1790, or earlier.
There are 129 records for Martins in the Tithes of the 1820s and 61 for Boylans. There are eight parishes where Martins and Boylans appear to co-exist, but very few where they are in the same townlands, and where that happens Given names appear to be irrelevant. I could not find the birth of a Richard Boylan in Ireland from 1740 to 1770. However, there were three births of a John Boylan in Meath from 1785 to 1795.
I will refer to Jane's reference to Dunshaughlin, and will add Rathregan, which is an townland within. However, I will also mention Ratoath, an area 6 kms to the east. It might be better to add the information :
BoylanChristopherBallybin BerfordRatoathMeath1828
BoylanChristopherCommons or Alleys FarmRatoathMeath1828
BoylanChristDartogueRatoathMeath1828
BoylanThosFlemingtownRatoathMeath1828
BoylanThosGlemingtownRatoathMeath1828
BoylanJohnGlemingtownRatoathMeath1828
BoylanChrisGlascarnRatoathMeath1828
All appear to be family names ( Thomas perhaps not)
It would appear that Richard Boylan may have married an Elizabeth Phillips (recorded as BOYLAND? ) in Nova Scotia in 1844. You will have to analyse material for accuracy, as I do not have your background. Hope something may help you.