do mini trees grow on bigger trees? tell me? inform me?

Indeed, they are called branches.

In a way, yes. In two ways, actually. In temperate forests, old trees fall down and decompose and they're root balls and rotting trunks serve as 'nurse logs' that fertilize new seedlings into saplings.

If during the growing process a tree develops two peak branches, they are grow up together, but both are the peak of the tree, like a two-headed tree. In adulthood, the two peaks can each reach the size of a tree, themselves.

One of these Split crowns came off of a neighbor's tree during a windstorm and landed not on the fence and the top missed my truck by 6".

It certainly FELT like a tree as I cut it up.