I've been dating my boyfriend for about three years, and from the beginning, I noticed that his testicles seemed smaller compared to others I've seen. However, everything functioned normally, except that he finishes a bit quicker than some of my previous partners. (But honestly, that is a blessing because after 2-3 hours I get sore. He actually considers me during sex instead of my previous partners who I started wondering if they were even attracted to me. I would feel like a sex doll with longer amounts of sex instead of a person, so this was a huge plus for me personally, and it's still a good amount of time with me and him.) His penis is of average size so I didn’t think much of it for a while. Basically my reason for explaining this is I noticed one thing strange down there but it didn't bother me at all for years because everything else was normal.
A few months ago, though, I looked up possible causes of small testicles, though I can't recall what prompted it. Anyway, his testes are about the size of 4-5 M&Ms each, and I can’t grab onto them at all or hold them in my hand. During my search, I found information about Klinefelter syndrome, and I can’t shake how well he matches many of the symptoms (except for reduced IQ or ADHD, though he does experience depression from time to time). He has very long limbs, narrow shoulders with wide hips, increased breast tissue, no facial hair growth, a female pubic hair pattern (an upside-down triangle instead of a diamond shape), and increased belly fat. The main symptom that stood out to me was the small testicles. I also read that the key symptom is infertility, but we haven’t reached the stage where we’re trying for kids or even engaged or living together.
Before I go on, I want to say that this condition wouldn't be a dealbreaker for our relationship. I unequivocally adore my boyfriend and am very attracted to heavier men. I'm quite small, so I enjoy being thrown around, and I love the extra heft during sex, cuddles, and even just aesthetically. I love fat men. I'm also not someone who believes biology determines your gender identity at all, and I respect and see him 100% as a man. But I’m also aware that, despite how sexy and handsome I find him, this could be a huge blow to his self-image and self-esteem. I want to navigate this carefully, if I approach the topic at all. I know he already has insecurities about his body, and some of them relate to the symptoms I mentioned, like not being able to grow a beard. Also, I could take or leave biological kids even though I do want to be a parent someday.
But more importantly than our relationship, I would feel so guilty if he were to find out he has this later in life and regrets not getting treated earlier, or feels like in general that he didn't know about a key part of his makeup until then. And I would be in his life still hopefully, but have to sit with how I hid this possibility from him so I didn't rock the boat.
I'm pretty sure he’s unaware of this possibility. A few reasons: I'm on birth control, but he jokes about how potent his sperm is and sometimes worries aloud about it failing. He also rarely goes to the doctor, likely because he grew up poor. (I did too, so I relate but I have adjusted in adulthood to go the recommended amount if I can afford it.) Even though he now has insurance through work, he still avoids going unless absolutely necessary. He’s also the type of person who would have told me if he knew he had something like this, especially since I’ve talked about wanting biological kids with him. He's also told me he has no idea why he can't grow facial hair, but just accepts it.
I’ve tried to push these thoughts aside because part of me feels it’s not my place to comment on his body, especially since I’m not a medical professional. But another part of me feels like I owe it to him to at least ask if he would want to find out if this is the case, so that he can consider testosterone injections as part of gender-affirming care, if that’s something he’d want. I’ve also thought about waiting until either A) we break up, and then tell him for the sake of his future, or B) we get married and try for kids, and then suggest we both get tested for fertility, using that as a way to discover any issues. In scenario A, he might be angry that I kept this from him for so long, but it wouldn't be as bad since we’d be breaking up anyway. In scenario B, I could at least act as if I didn’t know about Klinefelter until the fertility tests.
Or C, I could tell him now(ish).
How should I approach this, or should I just let it go since it might be disruptive to his life and self-image?
TL;DR: I think my boyfriend has Klinefelter syndrome (XXY chromosomes) because of his small testicles, body shape, and pubic hair pattern. He has no idea. How should I bring it up to him if at all?