Albizia - will a branch become a stem or trunk?

Thanks 

The trees are pretty common around here - the damaged one is a seedling from my neighbour's tree, and I have two more tiddlers in pots, so the loss wouldn't be a disaster. just a shame having got the tree that far!

Here's the top of my neighbour's albizia in full bloom - his garden is a few metres below ours so we get to see the blooms from above, arguably better than from below!

   

They can grow pretty big, either multi or single stemmed, but take pruning really well. There's a less common chocolate variety which is rather delicious, too