Well, he and Trudeau were best buds at McGill and Justin tends to favour hiring only those whom he already knows so it is not surprising that he might hire Butts.  As well, Butts has relevant experience as a former chief of staff to then Ontario premier McGuinty (awful experience in my opinion but undoubtedly impressive experience in Trudeau's opinion) and, more importantly, career long Liberal loyalties. 
And inasmuch as he and Trudeau are both in their mid 40s, I doubt if he is considered to be too young by Trudeau and his other handlers.

The only two people still living who meet your description are Harris and Peterson.  Obviously, the only viable choice from those two is Peterson given Mike Harris's strong political leanings and associations.

I suppose it is possible that Peterson is pulling the strings on this relationship but I doubt it.  If you have anything tangible to report, don't keep us in suspense.