A contraction of the words friend and mentor.
Friend - Person with whom time spent is mutually enjoyed.
Mentor - Person who can teach and, more importantly, inspire and motivate you.
A person who is both would be a frientor.
Lewis enjoys spending time with Rudy. Rudy is a couple of years older than Lewis, and can teach him things, while having a good time, because they have similar interests. This also causes Lewis to want to be better at the things that interest them both, in order to both impress and be more equal to Rudy in both confidence and expertise. Rudy is Lewis' frientor