When using parents and parents2 - families interspersed

[momack2]

When using both parents and parents2 within the same family - I end up with some weirdly interspersed relationships where current spouse (parents) and ex-spouse (parents2) with children are put very far apart from each other, which makes the whole graph more confusing:

I'd like it if all partners in 'parent' relationships were clustered as near to the central node as possible amongst other siblings. I've noticed that be reordering parent vs parent2 entries in my yml file changes this, but right now it's very trial and error. I'm not sure how to fix this (I'm concerned it's buried deep in the viz.js file), so if anyone has ideas I'm happy to help push on it.