Hello.
I am also a descendant of the Blacks of Breich Water. My 4x great grandmother was Margaret Black, daughter of John Black and Catherine Leckie/Lockie. She was born about 1803 and later married George Hamilton of Lesmahagow, Lanarkshire. The family migrated to Argyll about 1850. Their daughter, Elizabeth Hamilton, married John McMillan in 1856. That couple are my 3x great grandparents. I lived in that same area until immigrating to Canada as a small child with my parents.