pretty wild BikNut. Bare with me, I think the 12 yr old was some how you and MBs are a vehicle returning you to some thing unsettled if only the childhood wish to put an engine on a bicycle. A metaphor pertaining to the increasing responsibilities of growing? His older brother (guessing here, the voice of reason and responsibility?) advised you on some thing, might be the you who out grew it. "here" reintroduced you to old conflicting thoughts and required revisiting.
Or, I am just full o' sheep dip and it was just a rambling dream. lol, prolly the later. (but stuck in your head to the point of thinking about it at length)
I find most mornings I wake thinking about MBs. How to do some thing, build or how to make a bracket for a jet. Just the normal MB sort of stuff.