This is a little outdated, since I don't have this issue as much as I used to. But recently, I was reminded of it, and since I am on a personality/psychology forum, I might as well try to figure it out.
Throughout my entire life, up until a few years ago, I had this need to be someone's "right hand" person. I never knew why, but the desire was just there. It was definitely not a romantic or sexual thing. I don't think it was a parental thing either, since my parents are still together and have never been absent from my life. This was in its own category of human relations.
I first noticed it when I was in first or second grade. I had pretty bad anxiety even then, so I had short meetings with the school counselor. She just had this quality about her that amazed me. I would always be really excited to see her, to the point where I felt shy/embarrassed about how excited I was. I'd had crushes on cute boys, I'd tried really hard to get some of the popular girls to be friends with me, but this was entirely different.
When I first met my martial arts instructor (from ages 12 to like 16), I got the same feeling. More than anything, I wanted his approval. It was all I cared about for 4 friggin years. I actually planned on not going to college, and just teaching martial arts once I got good enough. After classes, I wouldn't want to do anything except sit/lay down and reflect on how much I loved being there. It didn't make sense to me back then, and it doesn't now. (Also, I left the class when I was the only one left and I saw that it was going nowhere. I also felt like I was being used. It took all of my strength to walk away, but I knew I had to).
It was to a much lesser degree, but I got the same feelings of admiration for one of the people in my D&D group when I was in high school. I just always wanted to impress this person for some reason. That didn't last long, since I sort of faded away from the two friends who encouraged me to join the group in the first place, and going after that would have been awkward. But I still remember that same intense nervous-excitement
That desire has pretty much fizzled out. When I started dating my first serious (and current) boyfriend, I had to grow up a lot, which required a lot of self-discovery. I started focusing on who I was, instead of focusing on another person's needs. I developed new hobbies/interests and developed a refined sense of self. Although my boyfriend is 5 years older than me, I don't see him in this mentor-ish light in any way. He is strictly a romantic partner and a friend.
Recently, I watched the Saw series. I was amazed at how much I identified with Amanda Young, John Kramer's accomplice who idolizes him the way I've idolized several people throughout my life. I read that she is an ISFP, and I think I am very likely an ISFP, so I am starting to think this might be type-related. I have also heard that this can be an enneatype 6 thing (I believe I am 6w7). If anyone has any ideas or has experienced this, themselves, please give some insight. It would be interesting to know if there are others who have had this "issue" or why I might have had it.