Well, I'm very sceptical about these things. I had something very similar with someone a couple of years ago.
We were finishing each others sentences, using the same odd turns of phrase as each other at the same time, and completely at ease by the end of the first date.
I read lots on here about relationships and one question that often gets asked is "how do you know if it's love?" and the response is often it's easy and feels like 'coming home' or "ah, I've been expecting you..." I had all of that with this man. I am very cynical. I don't believe in The One or love at first sight and I don't think that men are dopey hapless creatures who are unable to resist our feminine charms... but that's exactly how I felt about him.
We chose to take things slowly because of how intensely we felt about each other and didn't sleep together for about 2 months.
I met his parents who I got on with incredibly well immediately, they said that we were like the male/female versions of the same person. I've never felt like it about anyone before or anyone since.
I started to believe that, for the first time ever, I might have met someone who would, indeed, love me.
But 5 months after it started, I ended it. Because I realised it wasn't real. Any of it.
We have a couple of mutual facebook friends and I did, just out of curiosity, look at his fb page over Christmas, 18 months after I ended it and it turns out that within 4 weeks of us splitting up, he had changed his relationship status to "in a relationship" and when I had a quick look, it transpired that he was enjoying an equally intense and meaningful 'connection' with someone else within weeks of him being "heartbroken" by me!
The daft thing was that I had to text him after this new relationship had started because I found something of his at mine and was letting him know I was going to return it. I'd said "hi how are you?" in the message and he'd replied with, "still finding it hard, but taking it day by day" and he was loved up with his new girlfriend at the time!
I would be far more likely to trust someone who didn't do any of this shit, tbh. That would seem more genuine to me.