1901 census has him aged 88 - Date of Birth of 1813.    Found his death in the Deaths Index at Derry Family History Centre.  He was given as Robert Brewster, aged 93, Coleraine, 1.368, 2nd Quarter of 1904.  This changes his Date of Birth to 1811.   

Probably buried in Ballylintagh graveyard under stone inscribed, "To the memory of the Brewster Family of Dromore".   (See explanation of church membership under Mary Brewster.) 

Found his death in the Deaths Index at Derry Family History Centre.  He was given as Robert Brewster, aged 93, Coleraine, 1.368, 2nd Quarter of 1904.  This changes his Date of Birth to 1811.  The death entry, from Dublin General Registry Office, shows: 5th May 1904 Dromore, Robert Brewster,  widower, 93 years, labourer, debility and old age uncertified, Mary Brewster, granddaughter, Dromore, Present at Death. 

A death notice in the Coleraine Chronicle on 7th May 1904 also gave his age as 93 (no other details other than that he was from Dromore). 

Aged 75 in 1885 death certificate.

Date of Death found in Deaths Index in Derry Family History Centre.  Death certificate from General Registry Office, Belfast shows she was 75 years when she died  in Dromore, Macosquin on 8th July 1885, and that her daughter, Sarah Brewster, also of Dromore, was Present at Death.  Mary died from "old age and debility years - not certified no medical attendant".  She is given as the wife of a labourer.  The death was registered on 31st July 1885. 

Aged 24 when he married in 1866

Died of malignant tumour of the liver at 6 Quarry Place, Hamilton.

His mother is given as Mary Brewster, maiden name, Mary Boyd!!!!!!!!!!!!

His wife, Christina Brewster was PAD.

Given as 56 in 1901 census = Date of Birth of 1845.  220605 - email from Barbara Braswell, using Old Age Pension Census Enquiries, shows he thought he was aged 69 in 1917, when the enquiry was made = Date of Birth of 1848.  Response from Dublin Census clerks showing his age in 1851 census is almost lost in the fold, but it seems to be 8 = Date of Birth of 1843.  The 1911 census gives his age as 67 = Date of Birth of 1844.

Probably buried in Ballylintagh graveyard under stone inscribed, "To the memory of the Brewster Family of Dromore".  (See explanation of church membership under Mary Brewster.)  

Griffiths Valuation Revision Books show House 2Bc passing to Sarah Brewster in 1922, so he may have died around this time.

The death of a ROBERT Brewster, aged 81, in 1922 = DoB of 1841, is recorded in Civil Deaths and registered in Coleraine - unless this man was a Robert John, it cannot be this John.

Could this be him:
name:    John Bruster
registration district:    Coleraine
event type:    DEATHS
registration quarter and year:    Oct - Dec 1919
estimated birth year:    1846
age (at death):    73
volume number:    1
page number:    331
digital folder number:    4201711

Yep:
8th November 1919, Dromore; John Bruster; Male; Bachelor; 73 years; Stone mason; Heart Disease, certified; William J Gray, nephew, PAD, Garvagh.  So, no mention of him being called Boyd.

Age given as 53 in 1901 census = DoB of 1848 and 64 in 1911 = DoB of 1847.

Probably buried in Ballylintagh graveyard under stone inscribed, "To the memory of the Brewster Family of Dromore".  (See explanation of church membership under Mary Brewster.)  

Must have died post 1922 when the Griffiths Valuation Revision Books show her acquiring House 2Bc.  The Dromore Communicants Roll has her on its 1929 List but her name is then crossed out, which indicates she was alive in 1929 but died sometime thereafter and was crossed off.

Cannot find her death in Fs, FMP or GRONI

According to Coleraine Chronicle Obituary, she was 97 (= DoB of 1848) but this does not tie in with age given when married. The marriage certificate gives her as aged 28 when she got married on 16th March 1882 (= DoB of 1854). This would make her born in 1854 whereas the obituary makes her born in 1848. The 1901 census gives her as 47 so she was born in 1854 according to it!!  By 1911 her age is 60 (= DoB of 1851)!!  This one ought to be correct as it makes her 11 years older than the age her husband gives in the 1911 census (so she is no longer hiding the age difference, AND, she may well be wishing to claim the OAP and therefore needs to give her real age.  It is also a sort of average of the ages she gives.

Died at "Dun-Da-Bhann", Mountsandel, Coleraine - daughter Tilly's home.