Draw curved outline around two objects

Hello,
I’m trying to draw a shape similar to the one attached below, around two objects so that when these objects move away from each other, the shape changes with them as seen in the sequence below.
How would someone do that in unity? (Red shapes represent game object, black lines is what I want to draw)
114706-capture.png

So far I have drawn a circle around the two objects using LineRenderer but I am stuck at this point.

Thanks!

The most future-proof approach (say, if you need to ‘merge’ 2+N objects in the future) would probably be to go for a metaball approach : Metaballs - Wikipedia

Check this post for the philosophy behind building such structure : Metaballs and Marching Squares