What do you think

So I'm in one big friend group but I am only reeeally close to like 10 of them.
There that boy in the group who want to date me ,he want to meet my parents and all but we are not together yet we just act like we are (iykyk).
Only the 10 people know that and they told me that it has been 3 years that he is going out with that girl (I had a crush on but I'm not that close with) in the group ,they have already meet each other parents and all.
I am confused because last year she was going out with another girl and everyone knew that even him.
I'm not into casual dating I don't understand what they are playing at. I don't wanna be a third party. Is he playing with me? Or are they lying to me?
I'm embarrassed to ask the girl , because last time I overheard her saying how much she love him and all.