I was checking back on my records and found out that there were two Margaret Janes. One on the Montgomery side of the family and one on the Brown,s side,who would have been my dads aunt.
I have her being born 14/08/1890, and at some point lived at Agincourt Ave. MAY ?? have married a Robert Adams. Her family possibly lived in Pottinger ward when she was born.
I'm struggling so far to find a marriage for Robert Adams and Margaret Jane Brown, or a reference to either of them in Agincourt Avenue... HOWEVER, I could see the following couple of 1928 Belfast Telegraph 'in memoriam' notices for a Robert Brown of 143 Madrid Street who died in 1927, one of which mentions a daughter and son-in-law Margaret and Robert Adams:

The 1924 Belfast street directory on the Lennon Wylie website shows the following entry for Madrid Street:
143. Brown, Robt., rivetterThat 1927 Robert Brown death reads across to the following burial records for grave F3 195 in Dundonald Cemetery (ie. also the grave for a Sarah A Brown and Fredk Brown):
https://dof.belfastcity.gov.uk/burialsearch/BurialSearch.aspx?GraveSection=F3&GraveNumber=195&CemeteryName=Dundonald%20CemeteryThe Belfast Telegraph in 1966 carried the following couple of death notices for the Frederick Brown in that grave, they are a bit smudged, but I'm seeing 'son of the late Robert and Sarah Brown, Madrid Street, Belfast' and 'Deeply regretted by Brothers, Bill, George, Charles, James and Ernest and Families':

Does any of this ring a bell?