An expanding wellbore junction system, apparatus and methods are provided for forming a sealed wellbore intersection in a subterranean well. In one described method, an expandable wellbore junction is expanded within an under-reamed cavity in a wellbore. Intersecting tubular legs of the wellbore junction are then drifted using a drifting apparatus. A deflection device may be used to direct a drift of the drifting apparatus into a selected one of the wellbore junction legs.