This invention relates generally to an endoluminal prosthesis, and more particularly, to a stent graft assembly and method for treating branched vessels. The assembly includes a first pr sthesis, such as an iliac branch device (IBD), comprising a tubular main body, a first leg extending from a distal end of the main body and at least one fenestration formed in the main body. An internal tubular side branch extends proximally from the fenestration into the lumen of the main body, resulting in an iliac branch device having an overall reduced proximal length. The assembly further includes a second prosthesis, or a bridging limb, having a distal end with a scalloped fenestration formed therein to accommodate sealing with the proximal end of the iliac branch device without interfering with the internal branch. A connecting stent graft adapted for placement in the internal iliac artery may be sealingly connected to the internal branch.