Do we actually know of cases of people being disfellowshipped purely for keeping in contact with disfellowshipped relatives?
Here is the problem with that...
The true reprecussions of associating with a DF'ed person is getting "marked." Marking is an individual choice... this is why the literature contains highly guilt-based articles pertaining to "bad association." Bad association is a mystical thing in the Witness world... because social preference among humans is a highly complex animal.
The Watchtower doesn't want it to be simple, so they just change the reality of their members through the pages of the Watchtower. They paint us humans like "leaves in the wind." They teach children at a young age that we are highly impressionable... they teach that we are who we choose to associate with. This Witness prediction is self fulfilled though:
Witnesses are isolated from the outside world. "Being no part of the world" equates to almost complete isolation outside of Work or School...
Think about it... Witness children are trained to become blank slates. So if the conditioning is successful (because sometimes it doesn't take) then you have to make sure your subject is not placed in situations where someone else can "write on the blank slate" so to speak. Then you lose all the work put forth to capure a mind.
So, in regards to being DF'ed for associating with a DF'ed person. It might have happened but using the Witness Belief Framework I don't see it happening because the Marking Arrangement is so effecient.
Now if the Marking Arrangement is starting to become inneffective for whatever reason then you might see it more often.
-Sab