One of my greatest friends is a mere six years older than I am. She taught me Spanish for two years back in high school. Now we are so close . . . she has an apartment four blocks from mine and we frequently visit each other. While she still uses my surname (especially when she is frustrated with me), she likes it when I call her Anastasia. I do favours for her and she helps me out when I need a hand. We're there for each other.
And then there's my mother, a former teacher of mine. I daresay we are awfully close, as well.
(Good topic idea, Abu! Teachers are SOOOOOOOO unappreciated!)