Parallel links cross each other

I have 2 connected links between 2 nodes.
Since the nodes are close to each other, the links looks like they cross each other.
When i move one of the nodes to the right, you can see that the links are parallel.
I need them to be parallel also when the links are close to each other.
See attached pics.
Please advise.

There is currently no general feature that can do this automatically. However the Dynamic Ports Sample has an example of rudimentary custom link routing in order to keep links parallel when possible, which may be worth implementing for your case.

The nodes are tree layout (your recommendation)
How can i set (increase) the distance between nodes

That graph is not a tree, so perhaps using LayeredDigraphLayout might work better for you.

The TreeLayout.layerSpacing property controls the distance between layers.

i did used that LayeredDigraphLayout .
How can i force all nodes layed next to each other, side by side ?

LayeredDigraphLayout has both layerSpacing and columnSpacing properties.

What do you mean? A small screenshot of the problem and one of the desired results would help explain.