It sounds like you're not providing a decent environment for your sons to be fully honest with you. I doubt you'd ever know if either of them were anything other than cis and hetero.Yeah, my younger son and I have had quite a few talks over the years. Our love of music in general was a great way to steer the conversations into other topics too!
At one stage he was talking pretty negatively about girls and we had a lot of talks about stereotypes and how girls need to mature just as much as boys. Things like girls have certain types of peer pressure that boys don't have to deal with, an issue he hadn't thought of much... probably having only an older brother was a factor.
Several times he asked softly if I would have liked a girl, and I said NO! [and that is true - I was the tomboy]. I got worried after he subtly communicated that he questioned deep down because he wasn't as masculine and full-on logical like my older son [who is like my ex-soldier husband in personality] where he was overall.
I clamped down on that straight away, saying he was just different like I was - I had been a tomboy, I even had times I wished I had been a boy because boys seem to do more "fun things" and had way more comfortable clothes. He looked relieved that I said everyone should be themself, we shouldn't put ourself in a box etc, the world would be boring if we were all the same.
I wonder how many children around the world now been convinced they are trans or non-binary because they don't fit society's stereotype of male/ female EXACTLY. It makes me so sad, thinking of all the young people who will never be their actual true self, warts and all because of that.