Growing up I always had an inner monologue that was very clearly and obviously female despite me being biologically male and always identifying as cisgender, same age-range as whatever I was/am at the time, and I never thought much about it until I brought it up in my childhood to my family because I would refer to my inner voice as "her" and they thought I had an imaginary friend for the entire time up to that point.
My mom says her inner monologue has always sounded identical to her voice, and my brother doesnt have an inner monologue at all. Some folks I have asked about it state their inner voice sounds like them, sounds similar but the same gender as them, or doesn't have an actual voice and they just know what its saying in their head, but I havent ever met anyone who had opposite gender inner voice. Even my trans friends I spoke to say their inner voice matched their real voices, and changed as they transitioned.
Well in the past few years after a major health diagnosis, I found out I had a condition called tetragametic chimerism, where I had a twin in the womb who was a biological female who passed and got absorbed by me during gestation. I found out a lot of my organs have XX genetics, and its entirely possible my brain could have been impacted too. My psychologist believes it possible that could have caused my brain to develop a female inner monologue while externally I developed as a cisgender man, but considering its a rare condition that normally involves twins of the same gender, not opposite gender twins, I have never found another person who experiences this 😅.
So, does anybody else have that internal monologue that's the opposite gender as what you are externally? Ive always been curious about finding others who experience this too.