I was in the "I masked hard until I lost the structure going into uni" camp, and even then I didn't actually get a diagnosis until 31. It's super familial and looking back, my dad 100% has ADHD and kinda suspect my mom has ADHD too, it's not that they were in denial they just didn't see anything as atypical, no teacher ever flagged me either, again, hindsight, I was overly talkative to the point of distraction and absolutely had emotional disregulation.

My parents did their best and were supportive of me, it sucks I was late diagnosed but was not due to them at all.