It looks like a great opportunity to write a script. After all, it's all just maths; the names 'above' the root can evenly be distributed by dividing the available arc (180°) by the number of names (3), resulting in a separation of 60°, and the initial angle should be half that of that separation. So the first name is at 30°, the second at 90°, the third at 150°, and then there is a remainder of 30° again for the right side.
These same values should be used for the next layer of this onion (family trees can be smelly too), but this time I think the content should be centered on that angle, so the angle for each single line depends on the number of lines in that branch.
It sounds perfectly doable with a script, apart for one thing: how are you going to point out what texts must go where?