Hello reading your information I think there might be a connection.

My Great Grandmother was Isabella Jane Vannan (married to Andrew Johnston) - her parents were Elizabeth Sharp 23/3/1857 - 3/8/1938 & James Vannan (died 1918). The family have strong connections to Glasgow. This has not been my primary research line but I do have the following siblings related to Isabella Jane:
James Vannan married to Sarah McEwan
Daniel Sharp Vannan married to Jessie McIntryre
Helen Vannan