It's hard to know what people who have been in our lives and left retain of us. I'm constantly surprised at Christmas, the only time I see my grown stepnieces/nephews (I've been around their whole lives, their mother is my stepsister who I "met" before she was married) and occasionally they'll drop some memory from their childhood that was big for them but nothing much for me, a movie we went to or sleepover, etc.

I have 3 stepsons but they're still in my life but I identified with your story as my youngest stepson was 6 when I met him and always lived with his mom, only visited with us and is almost 30 now. He and I had some problems but we made some good memories too; lives are both I think and I try to remember that, that because I think of sad things doesn't mean there weren't many happy ones or that the other person doesn't have thoughts and memories of their own, different from mine, some better, some worse, etc. I like to believe that people enter our lives for a reason and when they leave they've fulfilled that. Too, I moved around my childhood and am familiar with people re-entering my life "later" so that's okay and a bonus, too. It can happen.