Is he truly single?

I’m seeing this guy that says that he’s single, but he’s also been “getting to know” another woman for almost two years now. They are always together, they frequently go on trips together (a few of them have been international), they are always each other’s plus one, and she’s met his closest friends and some of his family members.

However, he swears up and down that he is single. What do I make of this?
Is he truly single?
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