It was a rose grafted onto a root stock, the vigorous one on the right looks like the root stock, probably a simple briar.
I once had someone ask me to prune a very large old rose that was growing up the side of their house. They came back later in the summer and said it was flowering well, but the flowers only lasted a day, turned out the root stock had taken over completely, grown to about fifteen feet tall and I had pruned it beautifully.
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)