How is it possible for someone to enter your dreams?

There’s a guy I really like, and I’ve dreamed about him a lot. The dreams I’ve been having are those kind of dreams, if you know what I mean. I’ve had so many of them, and when I wake up I only remember images and emotions.
A couple of days ago he asked me if I’d dreamed about him recently (we’re super close, so it wasn’t too crazy of a question). When I told him that I had, he said that he had been awake and lucid dreaming in my dreams. I believed him a couple of months ago when he told me that it was normal, and said that he can go into people’s dreams at will or be basically dragged into people’s dreams. I’m extremely embarrassed now because the dreams were very explicit and apparently I dragged him into my dream and he remembers more than I do…
How the heck is this possible? Is this normal?