In the current version of yEd (3.10.1), when one uses the Family Tree Layouter on a larger family tree, the implemented algorithm tries to spread 'child nodes' roughly evenly relative to the 'parent node.' This in itself is not wrong, but often leads to unnecessarily large distances between the child nodes.
For 10+ generations and larger families the trees get rather wide and it is not uncommon that an edge connecting a child node to a parent node is as long as one third to one half of the width of the entire tree even though only one of the child nodes has further child nodes attached to it (simply speaking, only one of the respective child nodes is both a child and a parent node).
If the tree is smaller, spreading the child nodes evenly makes sense, but for larger and complex family trees such requirement forces the algorithm to produce wide-spread trees that are hard to follow (very long edges that often intersect etc.).
Would you please consider adding a checkbox to the Family Tree Layouter using which one could require child nodes to be as close to each other as possible? This way one could fine-tune the tree according to the actually produced layouts without any complicated decision logic being necessary in the application code.