Do the companion perks only apply when you have them as an active companion or once you have them as a companion do you keep their perk even if you switch comnaions? Also, I noticed that companion perks don't show up in my perk listings, is this correct or are they listed in your pipboy somewhere? If not, how do you check to make sure they are active?

No, when you get them you have them even if you bring another companion. Should be in the perk listing, atleast the one i got from Piper and Cait is there.

Hmmm...I have had 3 companions so far and no perk from them has ever been listed in my perks. Is it listed with the perks I got from leveling and magazines or should it be listed somewhere else?

Have you reached max loyalty with any of the companions? That is when you will get the perk. You will have a few convos with them as you adventure. When you reach max loyalty you will have an option to romance them if possible, otherwise you will just get a pop up saying you now have the special perk from that companion.

ahhhh...ok that must be it

Can you romance more than once? Like romancing Piper and Cait at same time?

Also do you lose their perks if they dislike you for whatever action you did?

Some people say yes, and some say no. There is no real reaction from Cait, but i think she will start disliking everything you do if you romance someone else. She is the kind of girl that wants a man/woman all to herself. Not sure about other companions yet. The game is still fresh and there is like 6 romance options to go through.