Notion Thief

[respawned]

If I have two {notion thief} in play, will I draw two cards for every one my opponent would draw?

[DrainCleaner]

No. There will simply be two redundant instances of a replacement effect.

[Giggle the Draco Genius]

Basically how this happens.

Opponent goes to draw.
Both {Notion thief}s see the draw.
They both try to replace the action.
When one replaces the action you are now drawing the card and the second does not have an action to replace.

[respawned]

Thank you