dfyx

In what way?

If you could change one thing about your job, what would it be?

Any particular reason why you chose this career? (Is career even the right word here?)

Never said that, never meant that.

When I said "inner child" I meant his own capability of leaving his adult responsibilities behind for a while in favor of doing things that society as a whole deems childish. Indulging in certain hobbies, acting a certain way. I can't find the right English word right now. In German we might call it being "unbeschwert", so maybe "unburdened".

I was specifically replying to the passage that he should have spent those 13 years in age difference growing as a person to an extent that he shouldn't have much in common with a 16-year old anymore. And to that I ask: why? Must every adult be a joyless, mindless worker drone who can't enjoy the things they enjoyed when they were 16? I'm happy to discuss if the relationship OP described might be problematic because of a power dynamic and that's been done to death in this thread. But saying he isn't allowed to feel connected to someone younger than him based on shared interests or a need to escape his adult responsibilities for a while feels bitter and judgemental.

None of this has anything to do with me labeling anyone as an actual child.

Edit: Maybe a picture says more than a thousand words so let me link to my favorite XKCD: https://xkcd.com/150/

Oh, don't get me wrong. It is a bit weird and concerning. But weird and concerning alone are not enough to stop something that's legal and at least for now seems to work pretty well. And like you said, not much they can do about it. The best course of action is to deal with it, be as accepting and supportive as they can and be prepared to help if things do go wrong. Everything else will make things worse.

Dude, what did you do in those 13 years to not grow as a person, ick. I can definitely understand why it would change your perception.

And comments like yours are the exact reason why he probably feels like he must protect his inner child against all odds. From what OP tells us, he has his professional life under control, so let him spend his free time however he wants. See my other comment for details.

What? That really shouldn't be the point for anyone to worry about.

The important thing is to make sure she's safe. As long as that is guaranteed, everything else is his choice and his responsibility. He is an adult, he is allowed to decide for himself if he cares about what society as a whole and his parents in particular think about him.

Shaming him and pressuring him into leaving her will only make him stick to her even tighter, just to spite everyone else. And that might actually go wrong when the relationship eventually breaks apart and he can't accept that because he doesn't have anyone else left.

Well, have you tried asking him why he picked her? Note my choice of words here. Specifically don't ask him why he didn't pick someone else but what he likes about her. My personal guesses (!) are: they share an interest in jazz music, they had a good time together at the festival and she doesn't expect him to act like society imagines "an adult": she lets him make up for something he missed when he was younger.

About her being hurt: he's your son, you know him better than we do. Do you think he's the kind of guy who would do that? If not, look out for signs that it might actually be happening instead of relying on your expectations. Stay in contact with her parents. At the same time, make sure she's comfortable talking to you. That way you will know if something happens. But please don't accuse either of them of something that isn't actually happening.

From your post, I can't quite decide what worries you most about this relationship... I've written and rewritten this comment multiple times because of that.

The usual concern with such an age gap would be that he might take advantage of her and her lack of experience. That's a valid concern that should be addressed. But It doesn't seem to be what's bothering you.

With you starting your post by telling us about his ex who is completely irrelevant to this story and your relationship with her, then later list off how great your son is and that "it’s not like he’s lacking options"... I can't shake the feeling that your problem is more with him having a partner that could be considered "below his own status". It feels like you would react just the same if he dated someone closer to his age but not as successful or good-looking. And to that I must say, that's none of your business. Let your son love whoever he wants to love. Let him make his own decisions and when it comes to it, his own mistakes. They obviously share some interests and he's old enough to decide if she's "good enough" for him.