With FNIS 5.0 Beta 1 modders now can add custom Paired Animations to the game.

1. Create a paired animation file (.hkx) in 3DS. Paired animtions contain the animation for both acors in one file. For details on how to create, see these two tutorials:
   http://http//www.nexusmods.com/skyrim/download/1000029814
   http://www.nexusmods.com/skyrim/mods/49311 by Kentington
   
2. Create an Animation Mod with a Animation List holding a line with the following
   pa -D
   e.g.
   pa -D3.466667 HugB paired_hugb.hkx
   
3. Run FNIS generator 5.1 Beta1 or later. This will create 2 AnimEvents, and pa_ (e.g. HugB and pa_Hugb)
   
4. In CK define one LOOSE Idle Object for the pa_ (e.g. Idle Object: pa_HugB with Anim Event: pa_HugB)
   
5. In your script run the animation with
   actor1.PlayIdleWithTarget(, actor2) (e.g. player.PlayIdleWithTarger(pa_HugB, Partner)
   All 3 character combinations (Player/NPC, NPC/Player, and NPC/NPC) are possible. Actor1 is the active actor. Which means s/he will teleport to actor2 before the actual animation begins, and then play the animation part 1.

Nice, now hopefully people will start remaking the animations that are meant to be paired.

I'm quite amazed by the work you've done with animations in Skyrim. Looking forward to see what people create with the new features.