jQuery, get Previous and Next element on Drag, based on parent -

I am trying to create a timeline, a dragger element and some dynamic build deadlines (DIVs) If you drag, it will indicate what is near the left and right viewer. The code works, you can see it. Just drag the red handle, the blue dot is left and the red is right.

The problem is that I need to get the next left and right element, whose elements are the same parent, the same layer Is there any way to do just what code is getting all keyframe elements from both layers? How can I achieve the next and the last element in which the same origin is?

Do you want it?

I separated the function which selects the keyframe nearest and then you send it to the container as a parameter for the layer.