Interesting question. Sharing a little is I experienced retrograde amnesia July of '78 when I was 24. Most of my memories when a child are photographs I memorized to have a base of understanding with family. Today my earliest recollection really is when I was in high school as earlier dates I am unclear of in the sense of remembering experiences contrast / compare with the photos and the stories I learned from family members.
So, that earliest most memory I have today is of an experience is say around my freshman year. It was delivering newspapers with a cousin some few years younger than myself. We had an argument, but later made up becoming great friends, even though we were of different families.
What an interesting question giving pause to ponder searching the mind to discover a memory of an experience, again contrasting a photo or a story told by a family member. I find it very interesting with your memory meeting your grandparents. How amazing that experience must of been. Realizing you both learned and assimilated the information of family lineage while trying to connect those dots surely that was a great adventure of discovery. That reminds me of when I did experience amnesia and asked "Who are you" to my family members when coming home from the hospital as really I had no idea who they were LOL . . .
Adding humor is a short story. When recovering I guess I began to stink a little not showering since the auto collision, of which the injury to the head occured some few weeks earlier. I remember my sister asking me if I would like to take a shower. I remember thinking 'What is a shower'.
Well my brother brought me into the bathroom and pointed out the bath tub while shared with me that is where i can shower. The funny part is he had to explain to me how to turn on the shower and what I had to do LOL. That was a fun filled first experience . . . showering. I bet they were relieved that I smelled like a fresh garden when done LOL :-)