i'm programming in python an application related to Tor with stem library.

when i create new paths sometimes the guard node (entry) belongs to the same family (group of servers) as the exit node.
 This is close to your case
the main problem that carries in both cases the connections can be analyzed based on time responses and patterns and being 'uncovered'.
Exist many studies about it, this is the last one i found and the newest, [link](https://mice.cs.columbia.edu/getTechreport.php?techreportID=1545) .

actually this can be an answer to your question : What is the risk of guard relay and exit relay being one and the same?