If you return one of the two fate bound creatures to your hand. Creature A still has to move closer to tile that creature B was last positioned on the map. When you replay creature B he's free from the enchant and can move wherever he wants. Creature A movement is still limited to that tile creature B was last on.

I haven't tried it with killing one of the two fate bound creatures, I'd guess though the same thing will happen. I'll try it later tonight if I get a chance and edit to let you know what happens when one of them is dead.

fixed