A stent-graft system includes a graft member and separate coupling stent that are adapted to be delivered separately to a location within a patient's body where they are coupled to form a stent-graft composite in-situ. The system thus allows for serial introduction of the graft member and coupling stent through an introducer sheath providing access to the location, instead of being delivered as the composite assembly together, thus allowing substantially reduced size of the introducer sheath. Particular embodiments provide highly beneficial improvements for treating AAAs, allowing for Seldinger puncture access techniques versus the conventional highly invasive "cut down" access procedures required by conventional pre-formed AAA stent-graft composite systems.