hi,
There is a Forbes BROWN and a Martha BROWN farming at Grogey c.1860.
I would guess that Martha is the Mother of Forbes, but can't be sure.
Martha would be a Widow, as that was the only way women could inherit land in those days.
There was also a John STEEN farming there, people never travelled far in those days looking for spouses.
There is only one BROWN in Grogey by 1901, she is a Widow and it looks like her daughter married George SYMINGTON.
There is a record of the FORBES/STEEN marriage, which means you could get a copy of the cert. from Roscommon.
That would confirm the Townland where the fathers lived.
Name: Forbes Brown
Spouse's Name: Eliza Steen
Event Date: 03 Dec 1857
Event Place: Lisnaskea, Ferm, Ireland
Spouse's Father's Name: John Steen
Here is the link...
https://familysearch.org/pal:/MM9.1.1/FGCN-WL9
Children of the marriage look like they were born in BROOKEBOROUGH,FERMANAGH,IRELAND.
There could be church records for births before 1864.
Birth of Forbes b.31 May 1866
https://familysearch.org/pal:/MM9.1.1/FRHY-68P
Death of Forbes 1944 in Penrith.
https://familysearch.org/pal:/MM9.1.1/FLND-6QH
Regards,
SEAN