I wish I could properly state the right of first sale he has, given it's his DNA (well, he has mine, anyway).
Fun fact: organs donated between perfect twins have no short- or long-term rejection issues. So unlike a regular donation that prolongs life for a decade or two, if he can drug me and steal my kidneys in sleazy Mexican motel, it's a permanent fix.
Hell, when I go, maybe he'll take a spare kidney or pancreas or something, and just, you know, hook them up. Totally fine with me.
Imagine taking everything. Splice both kidneys in there and get that ultra pure blood. Climb Mount Everest with no supplemental oxygen using a second set of lungs. Four nuts.