My ggg-grandmother Elizabeth Stevenson (c1861) was the daughter of Bridget Barret (c1835) and John Stevenson (born about 1836 in Paisley), himself the son of another John Stevenson and Elizabeth Harris (1813). John and Elizabeth Harris were married in Paisley in 1838.
I don't think our dates match, but I haven't come very far in placing my Stevensons yet. Who knows, they may have been cousins! I'll let you know as I find more about the family. So far I don't have any siblings at all.