Pretty sure my whole family knows. I've told this story a couple times, but I doubt it'd kill anybody if I told it again.
The first diapers I owned were girls' Goodnites. I didn't really hide them too well. I just threw them under my bed. Disposing of them was hard, so I'd keep used ones sealed in a ziploc bag until I could get them out discretely. So I had a couple ones I'd worn hidden after one night- a used one from the night before sealed in a bag, and one I'd worn but not used 2 nights ago. You can probably guess where this is going. My mom went in my room to clean, for whatever reason, and came across them. She discarded the 2 used ones, but didn't do anything with the pack itself. Found this out when I saw them sitting in the trash. Fast forward a few months, and I have another pack of Goodnites, plus some Depends w/ tabs. I didn't learn my lesson the first time and kept the same hiding spot. I went off to Scout Camp for a week. My parents come and pick me up at the end. After we get home, I go straight inside and find my diapers sitting out in the open in the kitchen. They found them, and I assume were planning on confronting me. I had another minute before they got inside, so I managed to get them back to my room (my brother was home, but fortunately, he was asleep on the couch). They never did confront me about it, fortunately.
So basically, odds are, my whole family knows. I guess they just don't want to know more and would rather not talk about it. TBH, I'm fine with that.