How to show that sentences in a paragraph are related

I have a paragraph with highlighted annotations. The user will be able to drag one annotation onto another annotation and I need to display somehow that the two are related.

I was thinking of adding a border to the left of each related annotation with the same color (see below). This seems a little too discrete though and also may get confusing if there is more than one related annotation for one text span.

The way that brat rapid annotation tool does it is very nice but I cannot do it that way in HTML (it uses all SVG).

Any ideas are greatly appreciated.