A stent graft system for intraluminal deployment in an aorta and a branch vessel includes an aorta stent graft for deployment within an aorta and defining a lumen for the passage of blood therethrough, and having a fenestration aligned so as to allow blood to flow to a contiguous branch vessel. A branch vessel prosthesis having a flaring portion, a tubular portion and an anchoring device, are configured so that, upon deployment, the tubular portion passes through the fenestration and into the branch vessel, the anchoring device affixes the position of the tubular portion within the branch vessel, and the flaring portion is retained within the lumen of the aorta stent graft and is maintained against an inside wall of the aorta stent graft to thereby bias the aorta stent graft toward the branch vessel.