Hi Allan,
My Great x3 grandfather was James Raeburn or Reburn, born in 1790 and his parents were James Raeburn and Isobel Stewart (or Stuart), who were married in 1779. They had five children in total, James, Jean, Barbara, Mardaret and Elspet. I got the details from the Scotlands people website, with a lot of help and guidance from people on rootschat. Henry Raeburn and Margaret Allan would be my 5Gr grandparents, so we must be 5gr cousins.
I've not come across Henry Raeburn snr and Margaret Castles yet so I'll see what I can find out about them.
All the best,
Rickr