My late wife and I finished each other's sentences. I always told folks after she passed that it came in handy when the brain tumor she had started taking it's toll on her. One of the symptoms that her tumor showed was something called aphasia, which was her not being able to say a word although she could see the word in her mind and knew it's meaning. You know when you say that a word is on the tip of your tongue? This was the real manifestation of it.
As for being able to finish each others sentences, I was driving with her and one of her friends. They were talking about something and I was half listening. Carroll was speaking and got to a spot where the aphasia kicked in, and without missing a beat snapped her fingers in my direction, I spoke the missing word and she kept on with the conversation. It was moments like that where I knew we were truly meant for each other.