Paired Opportunists

Whenever you are adjacent to an ally who
also has this feat, you receive a +4 circumstance
bonus on attacks of opportunity against
creatures that you both threaten. Enemies
that provoke attacks of opportunity from
your ally also provoke attacks of opportunity
from you so long as you threaten them
(even if the situation or an ability would normally
deny you the attack of opportunity). This does
not allow you to take more than one attack of
opportunity against a creature for a given acti