A stent graft includes at least one aperture extending through the main body thereof, into which an extension portion may be deployed for positioning within an adjacent branch flow lumen. The extension portions include self biasing features, wherein the extension is biased into engagement with the main body to seal the interface thereof. Additionally, the extension portion may be configured for tortuous or deviated anatomy, to enable sealing of the extension portion with the body while extending the extension portion in a substantially non-radial direction from the main body.