After dating for 4 years, he still won't introduce me to his friends!

From the start...

We've been dating four years now. He's 36 and I'm 22. Our relationship is mature, loving, respectful, and full of zest. (None of that "Sugar Daddy"...typical dating a twenty year old ditsy stuff)

I originally met his step dad before I met him. I met his entire family years ago and are very close with them. I know ONE of his friends relatively well (and by 'relatively' I mean he constantly calls at inappropriate times and tries to mooch as much as possible (he is 44!))

I know another of his friends, vaguely, and by this I mean he was a co-worker of my partners (we all worked in the same building, different businesses) and had lunch maybe twice. This friend is 25 years old and invites his long-time girlfriend every time they hang out (my boyfriend even tell his friend to bring his girlfriend). I've never been invited to anything (not even this friends moving-away party) even though random people from our office building who don't even know this guy were invited. (Side note : my boyfriend constantly decides last minute to drive three hours to visit this friend which isn't a problem, the problem is he tells me he's going to visit this friend, "just the two of them" for some guy time, and then I find out later that they have invited all of this friends friends, they're girlfriends, the neighbors, etc out for drinks (which my boyfriend will drop hundreds of dollars on so everyone will ahve a good time which does NOT impress me)

His other friend, well he's known him for 20 years, this friend is married with children, has a great job, etc. and knows all about me. My boyfriend tells me every time he goes out with him that him and his wife would love to meet me and have us over for dinner sometime. Has this ever happened? No. Would I like it to happen? Absolutely.

He has more friends than this but it hasn't started to bug me that I haven't met them yet. These three have been/are in his life constantly. And all of them invite there girlfriends/wife out when my boyfriend is around.

This was my first time dating an older man, and his first time dating a younger woman. So at first we thought it best not to mix this relationship with our friends (in case things didn't work out). That ideal changed along time least for me. He knows all my friends and they think he's the greatest guy in the world (don't get me wrong with this post, because he really is THE GREATEST MAN IN THE WORLD).

This is just starting to turn into a rant/ memoir...

My questions, after having read all of the necessary information, After four years, should I be concerned (because I am, and genuinely hurt) that he won't let me get to know his friends beyond they're names, ages, and professions
+1 y
Check your comments everyone! They don't give me enough characters up here to explain more so I've given you all a little more info. Can't wait to continue this(these) conversation(s).
After dating for 4 years, he still won't introduce me to his friends!
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