My Merry and Pippin (and Frodo too, for that matter, before he left) always know where one another are without looking. They never have to turn when one comes up behind them, and if that cousin knocks at the door to a room they are in, they know who it is without looking. It's just a little thing I have about the bond between the three of them.

And I love having the two couples being very close friends. I know two married couples, who have owned a home together for years. The wives think of themselves as sisters, and the husbands as brothers, even though they are not related. So I know that it is perfectly possible, even for humans, and for hobbits--who are far more social creatures--it should have been very natural.

Ah, so you know that Merry's problem with the mint in the bed is all too real! LOL!