two different key fobs in one prius

We also have two 2010 Prii. I often drive with both fobs in my pocket and haven't seen the problem. I have another friend with a 2010 and there are no problems when I ride with him or vice versa.
Thanks for the tip on the RFID chip. I had no idea.

 

I had the same problem with my Gen. II. When you have two or more fobs, sometimes they fight. Or sometimes they will synch up and flash their tiny red LEDs in unison. Stick one in a metal container with a tight fitting lid and it will shut up and stop bothering the car. An Altoids/Sucrets/cookie tin is fine.

 

My family has 2 2010 Prius IV. In fact, the only difference between the two of our cars is the exterior color. Mine is Classic Silver and my parents' is Winter Gray. I did this experiment the other day and have found absolutely no problems getting the doors unlocked and start either cars.

 

My friend's 2010 has this issue as well..when my key is on my person from my '12