A small number of minor-attracted people, mainly confined to the on-line bulletin board culture, have used the term young friend in reference to a younger companion of theirs.
Whilst some reserve the term for the younger friends who are closest to them, ongoing friendship with, and others use it more liberally to describe any significantly younger person they have contact with. To avoid this ambiguity the variant special young friend is sometimes used to refer to a close friend. Neither term necessarily refers to a sexual relationship.
The term "young friend" evolved as a play on the terms boyfriend and girlfriend and is usually abbreviated as yf (or syf for "special young friend") in writing. Online, it has mostly replaced the older terms "boy" and "girl" because many felt the phrases "my boy" and "my girl" sounded more possessive than "my young friend."