|That I know well, read my question carefully. Let's go trough it again:
Spoiler (highlight to view)
Poison got into Tenzen's body. Travelling with blood and lymphe (or simply by diffusion ), it should have got also to the twin. After all, twin's body was made from the same tissues as Tenzen's, so it had to have the same vulnerability to the poison. It should have died. Well, in the Shinobi movie Tenzen survived some wounds, but died ( just as his worms did ) from the poison
Still the bad cop.