My fishing and hunting partner is my five year old (wait a minute; this is his 6th birthday) Grandson. His big passions involve hunting, fishing, tools, soldiers; you get the drift.
When he was just starting to talk pretty good, my wife took him into the trailer house we have on our land to change a particularly lethal smelling diaper. When he came back out and saw me, he started yelling "Partner, Partner". No idea where that came from. He has never called me anything else and early attempts to change that to Grandpa or anything else would make him cry. He knows what partner means too. He talks about our pickup, tractors, stock tanks, land, rent houses, etc. He knows that the guns are mine but will be his someday. His parents have been in family court for a couple of years. There is Moms house, Dads house and our house or "home". We're the big permanent feature in his life and neither parent has a problem with that. He told someone the other day that we were buying more land but didn't know what we needed it for (sounds like Grandma is messing with his head). He didn't get to shoot his BB gun until he could name all of the parts. He still uses a push button reel but will graduate to a spin cast when his hands get large enough.
He has been practicing with his BB gun on a deer archery target for the big day coming up on the first full weekend in November. He has also been picking up forked sticks to practice his antler rattling. We will sit in a stand together and if a deer shows up, he gets the first shot with his BB gun and if they don't go down, I'll finish them off with my 30-06. This is his second year to hunt but last year we figured it might be imprudent to shoot anything since his Parents were in court and you never know what a liberal judge might do. This year; the heck with it.
BTW, Daisy makes a 30 inch BB gun called a Model 105B. The stock is 10 inches long. Just right for a small child and a guaranteed memory maker or bonding opportunity.