Hi,
I have one Forrest in my tree at the moment. She's not actually related to me, her daughter was my great-grandfather's first wife, but I thought I'd share in case her info is of use to you. Plus, while I'm 99% sure she's the mother of my great-grandfather's first wife, it'd be nice to see if you've got her on your website so I can double-check.
Anyway, I have a Catherine Forrest married to a William Nimmo in Blythswood, Lanark (abt 1857). I don't have any dates for their births but their son, William, was born about 1858. Following children were Elizabeth (abt 1860) and Catherine McInnes (abt 1862). Catherine McInnes married James Alexander (1869 - 1921). Either before or after the marriage, together or separately, the pair moved from Scotland to Ireland, specifically Londonderry. In Londonderry they had a daughter, Catherine Forrest Alexander, born about 1902. Catherine McInnes died the same year, either in childbirth or shortly afterwards.
Hopefully I haven't confused my Catherine McInnes's parents with another Nimmo/Forrest couple, but it seemed unlikely that it was a coincidence, with her daughter's middle name being Forrest.
Are they in your tree at all?