How to add relations to lines/curves between different sketches?

For example: 

Front plane and top plane are shown below.

I want to sketch on the top plane. There is already a sketched curve on the front plane. While in top plane, I want to be able to draw a line through the curve's endpoint. But when I hover over the endpoint (while in the top plane), the endpoint of the curve does not register or highlight, so I cannot add coincident relation or anything at all.

SolidworksUser Interface