Shared Memories

I guess we tend to assume that friendships are grounded on mutual memories of how you met each other, important moments in the friendship that helped to solidify it, etc. A couple of weeks ago, a friend of mine informed me that he couldn't remember how we met--a day which I remember with near perfect clarity, including the primary thing we discussed. I also remember, what to me, are key interactions along the way the eventually led us to becoming close friends that I suspect he does not. We do share at least one important memory, but not all. It made me question all the memories that I reflect on that provide me with affection for this person. I felt (and still feel) embarrassed that I reflect fondly on moments that seem to have little significance to the other person. (Though why I feel a sense of shame, I am not sure.)

I've had similar conversations with other friends and even my brother recently and on other occasions. I tend to take note when I am the one remembering something that the other person does not; however, I can recall instances in which I did not remember something that was important to another person. It seems to frustrate me more, the closer I am to the person. (For example, how can my brother simply not recall the stories about Gus the Friendly Ghost that my parents used to read to us?)

I know this is nothing new: do memories need to be shared in order to have importance in a relationship of any kind? Does this bother anyone else as much as it does me?