I have this, too - found out when I started doing astronomy and looking in the sky all the time. I also have a rarer one: the cough-ear reflex, which affects something like 2%. I involuntarily cough when I put in earplugs. The human body is weird!
That seems pretty reasonable/possibly explainable though. Putting eaebuds in deep I can feel a light gag reflex, ears and back of the throat are closely connected.
That's interesting if so, as I have some sensoneural hearing loss in inner ear, and had a period in past where I felt like was choking or some unexplained swallowing problems. Thought I was going bonkers when they couldn't find a problem.
I have the photic sneeze reflex too (didn't know there was a name for it!), and I've always known it was fairly common, but last summer I mentioned it to my grandfather, who had the opposite reaction as your father; he never knew it happened to anyone besides him! I wasn't aware he had it; he's my first relative that I've discovered has it as well.
I was shocked at the number of middle aged people who has never experienced heartburn. Around half of folks I surveyed. All the OTC anti-acid commercials led me to believe it was one of those conditions everyone suffered once in a while. Also surprising amount of people who never experience headaches.
I have photic sneeze reflex, hypnic jerk, and TIL exploding head syndrome. I associate hypnic jerk with a sensation of falling, whereas exploding head syndrome is a loud bang and bright flash. They both make you jump. I didn't know there was a different term for the loud bang/flash type.
I also have photic sneeze reflex but it only happens once per day when I expose myself to direct sunlight. Though typically I sneeze twice in a row and then it stops.
> People with the reflex tend to sneeze when they see bright things such as the sun.
I have this and I also sneeze every time I eat peppermint.
Do you or your father have deviated septum's? I ask as if you will actually know lol, apparently 80% of us have deviated septum's and there's a direct correlation between that and photic sneezers. I've had it for years but I only found out recently during a routine inspection that I do indeed have a deviated septum.
My septum was surgically corrected but I still have the sneeze thing.
Apparently this is very common with infants and young children. My two-year old sneezes in sunlight all the time. I mentioned it to our doctor (not because I was worried, just as an interesting comment) and he said most kids do this and some grow out of it.
I have it. Every daytime movie experience (that I haven't been to in a while) results in my sneezing 1-2 times. My ancestors must've evolved to live in some dirty caves. ;)
I had a similar experience when I learned that "aphantasia" is a thing (or rather, that having a "mind's eye" isn't just a figure of speech).
My father and I both have it, and it felt great when I told him about it. He was as surprised as I was that it didn't happen to everyone! In a weird way I'm grateful for it, as I'm sure the reflex urged me to stay inside and cultivate my love for computing :). It's too bad it made me dislike the beach as a kid though -- these days I make sure to bring sunglasses.
[1] https://en.wikipedia.org/wiki/Photic_sneeze_reflex