Field collection 'add more' and 'remove' hooks? I am currently working on a project where i have a content type that has 2 field collections. (with cardinality 1)
Each field collection has one other field collection (with unlimited cardinality).

To summarize:

Content type X


Field collection 1 

Some fields
Field collection A (unlimited cardinality)

Field collection 2

Some fields
Field collection B (unlimited cardinality)



Now,

I want field collection A and B to respond to each others "add item" and "remove" actions.
So that when you add an item to field collection A, automatically an item to field collection B is added as well and vice versa.

Are there any hooks available for this?

I have been doing some research but there is very little documentation about this that i can find.

Thanks so much in advance!
I managed to solve this with some jQuery. 

Not sure if this is the "cleanest" way to do this, but it works. I hook into the mousedown() event of the "add another item" button,and trigger the other button's mousedown manually.

I also added a delay of 800ms, because of some conflicting events if the 2 mousedowns are too quickly after eachother.

Hope this helps anyone in the future.

$('#edit-field-pressure-calculation-und-0-field-pressure-calculation-line .clearfix .field-add-more-submit').mousedown(function() {
    setTimeout(function() {
      $('#edit-field-heat-calculation-und-0-field-heating-calculation-line .clearfix .field-add-more-submit').mousedown();
    }, 800)

  });